Changing climate, increasing demand for potable water supplies and increased community interest for sustainable use of fresh water sources have resulted in a new focus on water use and sourcing. New sources are being sought, in conjunction with water demand minimisation strategies, to decrease the pressure on existing urban water resources. At the same time, the management of stormwater is being re-examined with the focus changing from the traditional practice of rapid disposal of stormwater (to reduce the risks of flooding) to utilisation of stormwater as an alternative water supply source. The focus of this thesis is the use of stormwater as an alternative supply source in urban areas at a cluster (or neighbourhood) scale. A decision making framework was developed to assist the adoption of a holistic approach to determining the most appropriate stormwater use scheme option. It was developed as an integrated planning tool to be used in the initial stages of investigating water sourcing and stormwater management ideas. Due to the time constraints of this project, the focus of the decision making framework was on the technical components (with associated issues) and financial costs. Since additional issues such as environmental, social and economic issues, are crucial to ensure a balanced view is taken in the decision making process, they are included in the process through additional information sources. Development of the decision making framework considered the following steps: • Development of stormwater use scheme options based on the technical components and associated issues of collection, storage, treatment, distribution and end use; • Development of screening tools to screen out infeasible or clearly inferior stormwater use scheme options; • Development of steps in the decision making framework; and • Demonstration of the decision making framework through the use of a case study. The decision making framework consists of eleven steps. The initial six steps of the decision making framework relates to collection and end use issues and are based around matching stormwater runoff to demand and matching stormwater quality to required quality. Steps 7 to 9 of the decision making framework consist of examining and determining feasible storage, treatment and distribution options. Step 10 of the decision making framework focuses on the integration of the feasible technical options identified in the previous steps, in order to develop stormwater use scheme options. The final step of the decision making framework is to determine costs of the stormwater use scheme options and compare the scheme options on the basis of cost, reliability of supply, quantity of stormwater utilised and end use demands met. The decision making framework was demonstrated as an easy and practical tool for determining the most appropriate stormwater use scheme through the use of a case study. An existing urban area was chosen as the case study due to the potential for the greater impact in terms of minimising potable water use for non-potable end uses. Feasible collection, storage, distribution, treatment and end use options were determined and integrated into 19 stormwater use schemes. Comparison of all the stormwater use scheme options, as well as the base case with no stormwater use, determined four options as being superior in terms of financial costs, reliability, quantity of stormwater used and end uses met. The decision making framework was developed based on existing constraints (such as the lack of guidelines directly examining stormwater use) and knowledge, while being flexible enough to include future scientific and practical knowledge, as it becomes available. Recommendations for future development of the decision making framework include expanding this decision making framework to identify the optimum scales of stormwater use schemes. Additionally, an effective yet simple to use costing tool needs to be developed so that all environmental, social and economic costs are determined and actual benefits of stormwater use schemes can be determined.

Electrical power systems utilise several voltage levels using power transformers to transfer voltages and connect parts of the power system with different voltage levels. One of these voltage transformations is being performed in the key component of the electrical power system: the distribution power transformer. It connects the Medium Voltage (MV) 11 kV - 33 kV networks and the Low Voltage (LV) 415 V networks, enabling connection of a large number of LV customers as well as (though to a much smaller extent) access of embedded generators to the electrical distribution network. Although the Australian distribution power transformers are considered to be very efficient devices (Minimum Energy Performance Standards - MEPS Fact Sheet, 2004), still roughly 3.2% of distribution transformers’ throughput electricity is lost due to their inefficiencies. The magnitude of these significant losses attributed to distribution transformers is a consequence of: • inefficiencies due to the design, materials and technologies used in distribution transformers; • inadequate type and rating of transformers selected for a particular application. The commitments of various Australian stakeholders (the public, the government agencies, distribution utilities, regulators, electricity industry trade associations, etc.) to limit emissions of greenhouse gases and to actively contribute to the global efforts to protect our environment are closely related to the energy market reform. The recent partial deregulation of the Australian electrical supply industry has introduced competition in retail and generation sectors and also significantly changed the operational environment for the electrical distribution companies. The era of increased competition for capital has commenced. The state based regulators have reduced incentives for over-investments, however, they still request enhancement of quality of supply and improvements of customer services. These, sometimes conflicting requirements have forced the electrical distribution utilities to move focus from improving economic efficiency of electricity supply and abandon long established practices for evaluation of distribution system performances applying multi-level economic analyses and systematic assessment of performances of key system components. It seems that “low initial cost” method (without proper assessment of total life cycle costs) is becoming much more attractive solution for selection of distribution equipment. The expected steady increases in energy demands and the need to undertake effective measures to protect the environment could be partially solved by improving energy efficiency of electrical equipment. The recent focus of the Australian government on the environmental costs associated with use of electrical energy has brought the efficiency of electrical equipment (including distribution transformers) under the spotlight. Highly efficient, yet cost-effective distribution power transformers, which are fully optimised for the expected service conditions (the likely load and the operating environment), are obviously the right solution for reduction of electrical losses. Introduction and use of such equipment would present significant challenge for electrical distribution utilities and private users of distribution transformers as this would have a considerable impact on their competitive position under the new industry structure. This research explores potential design improvements and increase in efficiencies for distribution transformers trough analysis of existing design and manufacturing technologies, relevant international regulatory developments, technological advancements and general trends in the context of the Australian market. It analyses the recently introduced mandatory Minimum Energy Performance Standards (MEPS) for distribution transformer and suggests courses of action for industry, regulatory bodies and the end users, which could help to ensure that those actions are part of the global solution for complex environmental issues. In addition, this research investigates a new two-stage approach for evaluation, assessment and utilisation of distribution power transformers and as such, to some extent, is directed towards a rational risk management and technical methodology to allow Australian electrical utilities and other interested parties to deal cost-effectively with present conventional technologies for distribution transformer used by major Australian manufacturers. The new assessment method for distribution transformers is based on: • development of cost efficiency schedules for selected designs and representative kVA ratings; • thorough financial analysis of distribution transformer losses. This refined methodology highlights importance of design and costing stages in the assessment process. Further, it recommends moving from simple capitalisation of transformer losses by extending evaluation of the total operating costs through introduction of new evaluation factors based on life cycle cost concepts and on expected service and loading conditions. This research is a contribution towards development of new procedures and methodologies, which will provide guidelines and recommendations for improvement of distribution transformer performances and increase compatibility of needs and capabilities of various stakeholders: end users, standards’ setting bodies, regulators, research organisations, equipment manufacturers, designers and consultants.

The objectives of this study were: 1) to investigate differentiation of Lactobacillus casei group by carbohydrate fermentation, PCR, gene sequencing and pulsed field gel electrophoresis, 2) to investigate tolerance of Lactobacillus strains in the presence of acid, bile salts and the or bile salt deconjugation, 3) to investigate viability of freeze dried Lactobacillus strains at various temperature during storage and their proteolytic activity, 4) to investigate the growth, viability and activity of Lactobacillus strains in skim milk containing prebiotics and 5) to investigate in vitro inhibition of Helicobacter pylori by Lactobacillus casei strains.

Sloshing is the low frequency oscillations of the free surface of a liquid in a partially filled container. The dynamic response of structures holding the liquid can be significantly influenced by these oscillations, and their interaction with the sloshing liquid could lead to instabilities. It is critical to predict and to control sloshing in order to maintain safe operations in many engineering applications, such as in-ground storage and marine transport of liquid cargo, aerospace vehicles and earthquake-safe structures. Contributions to the state of knowledge in predicting and controlling sloshing are the main objectives of the proposed research. To this end, a numerical model has been developed to enable reliable predictions of liquid sloshing. The numerical results are compared with experimental results to determine the accuracy of the numerical model. Further, the research addresses the employment of intentionally induced sloshing to control structural oscillations. The novelty of this research is in its use of a flexible container. Results indicate that intentionally introduced flexibility of the container is capable of producing effective control. The practical application of the proposed research is in the early design stages of engineering systems for which liquid sloshing plays a significant part in structural loading.

The zero-forcing algorithm (min-norm algorithm) is one of the proposed methods for downlink beamforming. This algorithm steers the nulls towards interferers and the main beam towards the desired user provided the angles of arrival of these signals are known to the basestation. However, downlink adaptive arrays use additional power when they are required to include null steering in their beam patterns. This excessive transmitted power reduces the effective antenna gain, increases interference in other directions and has implications on the dimensioning of the power amplifiers feeding the antenna elements. In addition, the power distribution among the antenna array elements is no longer equal. The design ratings for the power amplifiers (PAs) on each element can differ by up to 2.9 dB. A distributed amplifier design could solve this problem. This thesis investigates the trade-off of null depth with transmitted power and utility by modifying the zero-forcing algorithm. The performance or utility of the antenna is defined here as the probability that it can accommodate a given angular scenario between the desired user and interfering sources without transmitting excessive power. A -10 dB null increases antenna utility by 6% when steering a single null and 17% when steering 2 nulls if the excessive transmit power is held below 3 dB for a 4-element antenna array. In this work, a modified version of the min-norm algorithm was used to design the antenna weights from angle of arrival information.

Wireless communications has been so far largely based on centralized control, which in effect has limited its deployment, coverage and application scenarios. The paradigm of peer-to-peer wireless communications is fundamentally to remove this bottleneck and to further expand wireless communications into new applications. The technical and design challenges in implementing these networks are however plenty and exist in all the layers of the OSI protocol stack. In this thesis, we only consider the physical layer model of these networks. We identify multiple antenna systems as a vital component of physical layer solutions. We first investigate the case of multiple antenna space-time coding techniques to achieve spatial diversity. We observe that when correlation between the antennas in a local antenna array becomes high due to space constraints in a terminal, current performance achieving strategies do not actually deliver good results. Moreover, most mobile terminals are currently equipped with only one antenna. In view of this limitation, we study the recently proposed user cooperation techniques for exploiting spatial diversity with user power constraints for a simple three terminal network. We find that these systems are beneficial even with relatively simple protocols such as selection relaying. Finally, with simulation results, we demonstrate that the system performance can be improved significantly via near-to optimal selection relaying.

Substation Automation (SA) is a rapidly increasing area of interest in Electrical Engineering these days embracing numerous benefits to utilities. It is clearly the most dynamic and exciting new development in the substation industry with the ultimate goal of efficiently managing operations, maintenance and capital assets with minimal human intervention [1-4]. Intelligent Electronic Devices (IEDs), which are Instrumentation & Control (I&C) devices built using microprocessors, are the most important elements of a SA system. An IED is primarily used as a monitoring, control, protection or data processing device with at least a single serial communication interface. Substation IED networking requires the ability to remotely control, manipulate and monitor newly connected devices through the use of an effective communication system used to link various IEDs in a substation. The existence of a wide variety of vendor specific and hardware-oriented solutions as well as different communication techniques used for the communication between devices had previously stopped utilities from achieving a fully integrated and interoperable SA system. The idea of standardising the language of communication between IEDs has evolved as the key for the advancement of connectivity and interoperability within a SA system. As a consequence, Institute of Electrical and Electronics Engineers (IEEE) and International Electrotechnical Commission (IEC) have been developing SA standards based on Object-Oriented (OO) technologies. IEC 61850, the main topic of discussion in this thesis, is such a standard developed by the IEC Technical Committee (TC) 57. It describes how devices are to communicate in a substation as well as the related system requirements. It features support for all substation functions and their engineering with the use of OO data and service models [5]. However, it has only been abstractly modelled meaning that it focuses on describing what the OO models are indented to provide rather than how they are built. Consequently, the IEC 61850 standard can only be operational when mapped to a specific concrete application layer protocol such as the Manufacturing Message Specification (MMS) or ISO/IEC 8802-3, which are the two communication services put forward by the IEC 61850 standard. The primary objective of this research is the OO implementation of the IEC 61850 standard as a concrete application layer protocol running on a middleware platform designed and implemented in a communication processor environment. In this research, the IEC 61850 implementation is founded on the C/C++ programming language development of the standard’s Abstract Communication Service Interface (ACSI) Object and Service Models (OSMs) as concrete programs based on their published definitions, hence transforming the IEC 61850 standard into a solid protocol. An alternative to the present implementation practice, the mapping process as proposed in the IEC 61850 standard, is recommended where virtual representations of real devices can be modelled and implemented at the application layer of a communication processor making use of the OO implemented OSMs of the standard itself rather than using the equivalent models of another application layer protocol. Middleware is a software layer that resides between the operating system and the applications allowing multiple processes running on different machines to interact over a network. Middleware design is based on architectural issues concerned with the organisation, overall structure and communication patterns dictated by applications as well as the middleware itself [6-7]. This thesis describes the design and implementation of a new middleware architecture aimed at providing diverse communication methods to IEC 61850 related applications. The designed middleware is of the Message-Oriented Middleware (MOM) category and considers the fact that communicating entities may take on different roles such as client/server or peer-to-peer, therefore allowing for different interaction modes such as synchronous invocations and asynchronous message passing. Several simulation studies are also presented in this thesis to demonstrate how IEC 61850 applications can be built at the application layer of a communication processor as well as to test and evaluate the performance of the middleware architecture implemented within the same communication processor environment. Time synchronisation, which involves synchronisation of the date and time of all devices in a network, is another key topic discussed in this thesis. Time synchronisation is crucial in time-sensitive substation applications and its importance has been clearly acknowledged by the IEC 61850 standard as a requirement. The implementation and integration of the Simple Network Time Protocol (SNTP) and its applications into the overall communication processor architecture is another feature proposed in this thesis in order to facilitate the time synchronisation of applications designed in this research. Ultimately, the development of a gateway capability that permits for the testing and evaluation of the designed components over a real network is described. The designed and implemented "Hardware in the Loop" (HITL) capability mainly provides the necessary interface between the real Ethernet network and the simulation environment enabling two or more simulations running on separate computers to be linked together.

This study investigates the experiences of first year engineering students to a newly implemented engineering problem-based learning (PBL) curriculum at Victoria University; its effects on their approaches to learning and their learning outcomes. This qualitative study, which uses ethnographic approaches for data collection and analysis, focuses on the learning cultures that emerge in multicultural PBL teams by interpreting the responses of students to the new emphasis on autonomous learning. In the first year of the curriculum change in this PBL setting, this research captures and theorises student approaches to learning as a team and their learning outcomes by analysing the ways in which these students approach and direct their learning as individuals and as a team.

This thesis presents investigations aimed at obtaining a system model for the stabilisation of an Active Magnetic Bearing (AMB) System. Furthermore, the study reported here set out to design both conventional and advanced controllers based on the system model. This research report demonstrates that the literature on AMBs shows that AMBs are making their mark in the industry; they are increasingly being used in applications including jet engines, compressors, pumps and flywheel systems. In this study, it has also been observed that the basic design of AMBs is an arrangement of electromagnets placed equidistant in a ring round a rotor. The point of departure for this study is that AMBs are highly nonlinear and inherently unstable. Hence, the need for an automatic control to keep the system stabilized. The first step of the research was to determine the transfer function of the MBC 500 magnetic bearing system both analytically and experimentally. An analytical model has been derived based on principle of physics. As the AMB system under analysis is inherently unstable, it was necessary to identify the model using a closed-loop system identification. Frequency response data has been collected using the two-step closed loop system identification. As there are resonant modes in the MBC 500 magnetic bearing system, the system identification approach has identified the corresponding resonant frequencies. Subsequent to obtaining the model, a conventional controller was designed to stabilise the AMB system. Two notch filters were designed to deal with the magnitude and phase fluctuations around the two dominant resonant frequencies. The designed conventional controller and notch filters have been implemented using MATLAB, SIMULINK and dSPACE DS1102 digital signal processing (DSP) card. Both the step response and robustness tests have demonstrated the effectiveness of the conventional controller and notch filters designed. A significant conclusion has been drawn when designing the conventional controller. It was found that a controller that had a large positive phase angle had a negative effect on the system. This finding was very significant because it restricted the controller specifications and yielded an optimum lead angle for the conventional controller. The advanced PD-like Fuzzy Logic Controller (FLC) has also been designed for AMB system stabilisation. The designed FLC can deal with the magnitude and phase fluctuations around resonant frequencies without using notch filters. The performance of the designed FLC has been evaluated via simulation. Simulation results show that the FLC designed leads to a reliable system performance. Comparison studies of the FLC performances with two different sets of rules, two different inference methods, different membership functions, different t-norm and s-norm operations, and different defuzzification were investigated. To further improve system performance, scaling factors were tuned. Again, simulations showed highly promising results. Comparative studies between the conventional and advanced fuzzy control methods were also carried out. Advantages and disadvantages of both approaches have been summarised. The thesis has also suggested further research work in the control of AMBs.

Micro-organisms possess endogenous enzymes, however, the stability of these enzymes during storage in soymilk has not been studied. β-glucosidase is an important enzyme that could be used in the bioconversion of the predominant soy isoflavone glycosides to their bioactive aglycone forms. Fifteen probiotic micro-organisms that included Bifidobacterium sp., Lactobacillus acidophilus and Lactobacillus casei were screened for β-glucosidase activity using ρ- nitrophenyl-β-D-glucopyranoside as a substrate. Six strains were selected on the basis of β- glucosidase activity produced during fermentation of soymilk. The stability of the enzyme activity was assessed during incubation for up to 48 h and during storage for 8 weeks at frozen(-80°C), refrigerated (4°C), room (25°C) and incubation (37°C) temperatures. L. casei strains showed the highest β-glucosidase activity after 24 h of incubation followed by L. acidophilus strains, while Bifidobacterium strains showed least activity. However, β-glucosidase from Bifidobacterium animalis BB12 showed the best stability during the 48 h fermentation. Lower storage temperatures (-80°C and 4°C) showed significantly higher (P<0.05) β-glucosidase activity and better stability than that at higher temperatures (25°C and 37°C). The stability of β-glucosidase from these microorganisms should be considered for enzymic biotransformation during storage, of isoflavone β-glycosides to bioactive isoflavone aglycone forms with potential health benefits. Three strains of L. acidophilus, two strains of L. casei and one strain of Bifidobacterium were screened for β-glucosidase activity using ρ-nitrophenyl-β-D-glucopyranoside as a substrate and their potential for the breakdown of isoflavone glycosides to the biologically active aglycones in soymilk. Isoflavones quantification with HPLC and β-glucosidase activity was performed after 0, 12, 24, 36, and 48 h of incubation in soymilk at 37°C. All 6 microorganisms produced β-glucosidase, which hydrolysed the predominant isoflavone β-glycosides. There was a significant increase in the concentration of isoflavone aglycones and a subsequent decrease (P < 0.05) in the concentration of isoflavone glycosides in fermented soymilk. Based on the concentration of isoflavones during peak β-glucosidase activity, the hydrolytic potential was evaluated. L. acidophilus 4461 had the highest aglycone concentration of 76.9% after 24 h of incubation, up from 8% in unfermented soymilk (at 0 h). It also had the best isoflavone hydrolytic index of 2.01, signifying its relative importance in altering the biological activity of soymilk. Soymilk fermented containing soy isoflavones with B. animalis Bb12 was stored at various temperatures (-80°C, 4°C, 25°C and 37°C) for 8 weeks and the concentration of isoflavones determined weekly using RP-HPLC. The first order kinetic model was used to assess the degradation of each isoflavone isomer at each storage temperature. During storage at various temperatures, concentrations of individual isoflavone isomers appeared to be significantly stable (P<0.01). Interestingly, the aglycones showed much smaller degradation constants as compared to the glycosides at all the storage temperatures. Genistein and daidzein were much more stable than glycitein and had almost similar degradation pattern, despite differences in their concentrations in the fermented soymilk. It was, however, observed that 4°C was the most suitable storage temperature for the product as there was a minimal degradation of bioactive isoflavone aglycones. Three selected L. acidophilus strains were used in the fermentation of soymilk and then stored separately at various temperatures (-80°C, 4°C, 25°C and 37°C) for 8 weeks and the concentration of isoflavones determined weekly using RP-HPLC with diode array uv visible detector. The decreasing concentration of isoflavones in soymilk during storage due to degradation was found to fit first order kinetic model. Isoflavone aglycones as well as isoflavone glycosides largely appeared to be stable during storage (P<0.01). Interestingly, the aglycone forms showed much smaller degradation as compared to glycoside forms at all the storage temperatures. Of the isoflavone aglycones, daidzein was most stable followed by genistein, while glycitein was least stable. Isoflavone aglycones such as glycitein, daidzein and genistein showed smaller degradation constants in fermented soymilk at lower storage temperatures (-80°C and 4°C) and higher degradation constants at higher storage temperatures (25°C and 37°C) with each strain. In contrast, glycosides glycitin and daidzin showed higher degradation at lower storage temperatures (-80°C and 4°C) and lower degradation at higher storage temperatures (25°C and 37°C). Storage temperature was therefore found to be very important in regulating the rate of degradation of soy isoflavones in fermented soymilk. The degradation of each isoflavone compound in soymilk fermented with 2 Lactobacillus casei strains and stored at various storage temperatures (-80°C, 4°C, 25°C and 37°C) was evaluated and again found to fit the first order kinetic model. All isoflavone compounds in the soymilk appeared to be generally stable during storage (P< 0.01) at all storage temperatures. Aglycone forms however, had smaller degradation constants compared to glycosides at all storage temperature in the presence of each of the micro-organisms. Specifically, aglycones showed a unique trend of smaller degradation at lower storage temperatures (-80ºC and 4ºC) than at higher temperatures (25ºC and 37ºC). Glycoside genistin was least stable at all storage temperatures compared to other isoflavones, while aglycone daidzein was the most stable. L. casei 2607 in fermented soymilk stored at 4ºC after 8 weeks gave the least degradation for daidzein of a mere 3.78% loss from 9.53 to 9.17 ng/µL. L. casei 2607 showed greater hydrolytic potential than L. casei ASCC 290 as denoted by higher degradation of isoflavone glycosides in fermented soymilk at lower storage temperatures. The optimum storage temperature offering least degradation of bioactive isoflavone aglycones in fermented soymilk was found to be 4ºC. Liquid chromatography coupled with positive electro spray ionisation tandem mass spectrometry (MS/MS) and diode array detection was used for the quantitation and characterisation of isoflavones in fermented and unfermented soymilk made from soy protein isolate SUPRO 590. Bifidobacterium animalis ssp. lactis Bb12 was used for the fermentation of soymilk. The isoflavones were found to produce characteristic radical ions as well as molecules of H20, CO2, a sugar unit, and an alcohol through collision-induced fragmentation. Product ion fragments revealed unique fragmentation pathways for each isoflavone compound. Characteristic fragmentation of different isoflavones were unequivocally identified and differentiated. The occurrence of aldehydes such as pentanal, ethanal and methanal was shown to be specifically linked with isoflavone aglycones, daidzein, genistein and glycitein, respectively. Main glycosides such as genistin, daidzin and glycitin as well as the acetyl-, and malonyl forms also showed respective aglycone ions in their spectra fragmentation. Thus positive ion fragmentation was important in the unequivocal confirmation of isoflavones and for revealing the occurrence of other related compounds such as aldehydes in the soymilk. Comparison of endogenous β-glucosidases and β-galactosidases in selected probiotic bacteria as hydrolysing enzymes in the breakdown of the predominant isoflavone glycosides in soymilk into bioactive isoflavone aglycones is critical for an optimised processing of a probiotic functional food. β-glucosidase activity and β-galactosidase activity of probiotic organisms including L. acidophilus ATCC 4461, L. casei 2607 and B. animalis ssp. lactis Bb12 in soymilk was evaluated and correlated with the increase in concentration of isoflavone aglycones during fermentation. The concentrations of isoflavone compounds in soymilk were monitored using a Varian model HPLC with an amperometric electrochemical detector. In all microorganisms, β-glucosidase activity was found to be greater than that of β-galactosidase. The aglycone concentration in the soymilk with L. acidophilus 4461, L. casei 2607 and B. animalis ssp. lactis Bb12, increased by 5.37, 5.52 and 6.10 fold, respectively after 15 h of fermentation at 37ºC. The maximum hydrolytic potential was also observed at 15 h of fermentation for the three micro-organisms coinciding with peak activities of the two enzymes. β-glucosidase activity was found to be more than 15 times higher than that of β-galactosidase activity in the soymilk for each microorganism during fermentation. It appears β-glucosidase played a greater role in isoflavone hydrolysis. It is important to determine critical parameters such as which hydrolysing enzyme have a greater impact in the development of a probiotic functional food beverage. In this case it is essential to enhance β-glucosidase activity for its greater role in improving the biological activity of soymilk during processing. Having established that endogenous β-glucosidase plays a greater role in isoflavone biotransformation, it was essential to compare endogenous and exogenous β-glucosidases for their role in isoflavone biotransformation. β-glucosidase activity of probiotic organisms including Bifidobacterium animalis ssp. lactis Bb12, Lactobacillus acidophilus ATCC 4461 and Lactobacillus casei 2607 in soymilk was evaluated and found to relate to the increase in concentration of isoflavone aglycones during fermentation. The concentrations of isoflavone compounds in soymilk were monitored using a Varian model HPLC with an Amperometric electrochemical detector. The aglycone composition, also known as aglycone equivalent ratio, has been considered to be important for delivery of health benefits of isoflavones, was also monitored during fermentation of soymilk. Comparison of the hydrolytic effectiveness of both exogenous and endogenous enzyme during 4 h incubation in soymilk was conducted using the Otieno-Shah (O-S) index. Results showed that exogenous enzyme exhibited faster rate of isoflavone glycoside hydrolysis than that by endogenous enzyme. Highest O-S indices were obtained after 4, 3 and 2 h of incubation with enzyme solution having β-glucosidase activity of 0.288 UmL-1, 0.359 UmL-1, and 0.575 UmL-1 resulting into aglycone concentration increments of 5.87, 6.07 and 5.94 fold, respectively. Conversely, aglycone concentration in the soymilk with B. animalis ssp. lactis Bb12, L. casei 2607 and L. acidophilus 4461 increased by 3.43, 2.72 and 3.03 fold, respectively after 4 h of fermentation at 37ºC. Also, the O-S index of endogenous enzyme was much lower than that of the exogenous enzyme over the same 4 h incubation period. Optimum aglycone equivalent ratios coincided with highest O-S indices and highest aglycone concentrations in soymilk hydrolysed with exogenous enzyme. The same correlation of O-S indices and highest aglycone concentrations occurred for endogenous enzyme during the 24 h of fermentation. Therefore, obtaining highest aglycone concentration as well as optimum aglycone equivalent ratio could provide a critical beginning point in clinical trials for maximum realisation of the unique health benefits of soy isoflavones. Screening for β-glucosidase activities of probiotic bacteria in soymilk as well as comparing their hydrolytic potentials with that exogenous β-glucosidase could find wide applications in the development of different aglycone rich functional soy beverages.