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The maximum potential of biorefineries cannot be achieved without the valorisation of their residues. The two main residues from wheat biorefineries, bran and wet distiller's grains and solubles (WDGS), have a projected production of 7 and 3 million tonnes/year respectively by 2025 just in the European Union. These residues can be mixed to form moist animal feed. However, the product can undergo growth of contaminating fungi. This bio-deterioration causes significant losses and represents a hazard for the animals. Currently, commercial preservatives (from the petrochemical industry) are added to prevent bio-deterioration but these add to the production cost. The research reported in this thesis was focused on the utilisation of solid state bioprocessing (SSB) to prevent the bio-deterioration of the moist feed. The method is based on the inhibition of contaminating fungi by an edible fungus, R. oryzae, considered safe for animal consumption which is a lactic acid producer. This fungus is known to produce very dense mycelia causing significant oxygen transfer limitations and this, together with the reduction in pH and substrate available for contaminating fungi, was explored as a potential mechanism to bio-preserve the moist feed. SSB, has been targeted as a key technology for the treatment of agro-industrial solid residues. However, the measurement of parameters in SSB is very complicated, hampering the development of the technology. Consequently, methods for the measurement of pH and growth in SSB were also studied. The measurement of pH is normally performed in extract solutions but, although widely used, the method has not been standardised. There are many extraction variables, such as contact time, type of solids and solvent, solid:water ratio and agitation velocity, involved in the measurement. Experiments revealed that changes in the extraction conditions affect pH readings. The degree of impact depends upon the variable but results presented in this thesis clearly highlight the importance of providing a precise and comprehensive report of the extraction conditions. For the estimation of growth, a method based on digital imaging analysis (DIA) was developed in this work. DIA is a non-destructive, quick and simple method, which uses computational analysis of digital images to measure areas and colour changes on a surface. The technique provided data that allowed an objective comparison of fungal colonies on plates, making it of higher quality than simple visual evaluation. It was determined that C*Traffordgold, the model moist feed used in this research, has starch and moisture contents of 10% and 50% respectively. Bio-deterioration is caused by indigenous organisms in the bran and is observable after only 2 days of incubation at 20°C. R. oryzae was able to bio-preserve the material for at least a month. This is a very promising result since preservative treated C*Traffordgold shows considerable bio-deterioration after just 2 weeks. DIA was used for the estimation of R. oryzae growth at different temperatures, moisture contents and inoculum sizes. The fungus was able to grow at temperatures between 15° and 37°C, with optimum growth at 30°C. An increase in the moisture content resulted in faster growth of the fungus and it was determined that a minimum inoculum size of 103 spores/gC*Traffordgold is necessary to avoid bio-deterioration. The bio-preservation is a result of the reduction of substrate and oxygen available for contaminating microorganisms. Studies revealed that lactic acid does not inhibit growth of contaminating fungi even at pH 4. On the other hand, R. oryzae showed radial growth rates up to 6 times faster than those from contaminating cultures. The fungus is able to surround the competitor colony and 'enclose' it. The formation of a fungal barrier limits the oxygen available for the undesired colony, hampering its growth. It was estimated that by implementing the bio-preservation method a wheat biorefinery producing 180,000 tpa of moist feed could save circa 500,000 USD per annum. Integration of residue processing in biorefineries is necessary to make them sustainable. The application of SSB for bio-preservation could enhance the overall value of wheat biorefineries and simultaneously reduce dependency on the petrochemical industry.

La sicurezza e la qualità degli alimenti sono tutt’ora un problema critico per i paesi in via di sviluppo. Le diete a basso contenuto di acido folico, per esempio, possono causare gravi problemi di salute, soprattutto nei bambini. Gravi disturbi legati al tubo neurale (DTN) nei neonati possono derivare infatti da madri che hanno insufficiente apporto di acido folico (400-600 g / giorno) durante il periodo di gravidanza. Inoltre, se non adeguatamente protetti o trattati, I prodotti alimentari possono essere vettori di funghi e batteri patogeni rappresentando una fonte potenziale di malattie per l’uomo e una perdita economica per le industrie agro-alimentari. Nella seguente tesi si è quindi quindi studiato il ruolo di batteri lattici selezionati (LAB) in grado di aumentare il valore nutrizionale del latte attraverso la produzione di acido folico durante il processo di fermentazione. Inoltre, ci si è concentrati sul loro uso come "bio-conservanti" contro funghi e batteri, attraverso la sintesi di composti antimicrobici (batteriocine) in grado di inibire la crescita di funghi filamentosi e/o batteri patogeni. / The safety and quality of food are still a critical issue in developing countries. Diets with a low content of folic acid, for example, may cause serious health problems, especially in children. Severe disorders related to neural tube (NTD) in infants may arise from mothers having inadequate intakes of folic acid (400-600 g/dia) during the mother pregnancy period. Moreover foods, when not properly protected or treated, can be vectors of pathogenic fungi and bacteria thereby representing a potential source of human diseases and an economical loss for the food industry. In the following thesis we have therefore investigated the role of selected lactic acid bacteria (LAB) in increasing the nutritional value of milk through the production of folic acid during the fermentation process. In addition, we focused on their use as “bio-preservatives” against fungal and bacterial spoilage, through the synthesis of antimicrobial compounds (bacteriocins) able to inhibit the growth of filamentous fungi and /or pathogenic bacteria.