Magister Scientiae - MSc / Alternative sources of fuel are required worldwide, and bio-ethanol is the leading candidate. Lignocellulosic biomass, a waste component of the agricultural industry, is a promising renewable source. Due to its complex structure it is highly recalcitrant, requiring the synergistic action of a battery of enzymes to achieve complete digestion. These enzymes include cellulases, hemicellulase and the accessory enzymes acetyl xylan esterase (AXE) and ferulic acid esterase (FAE). Thermpohilic Actinomyces isolates with the ability to hydrolyze xylan were screened for esterase activity. Two isolates (ORS10 and GSIV1), identified as Streptomyces spp, were positive for AXE activity. A cosmid library representative of isolate ORS10 was composed and screened for AXE activity using -naphthyl acetate as substrate. An 18 kb cosmid clone, 18D7, tested positive for AXE activity. Intracellular fractions extracted from ORS10 were precipitated with ammonium sulphate and partially purified 161-fold. Specific activity was measured after dialysis and ion-exchange chromatography. Overall yield of the partially purified enzyme was 34 %. Two protein bands of molecular masses 40 kDa and 60 kDa have been subjected to trypsin digestion and MALDI-TOF mass spectrometry analysis. The partially purified AXE displayed optimum activity at pH 9 and at 50°C. AXE activity was stable for at least 1.5 hours between 30°C and 40°C, and for 24 hours between pH 6-9. The kM and Vmax values were 16.93 mg/ml and 1645 units/mg enzyme, respectively. The stability of the partially purified AXE at 30°C-40°C suggests potential for industrial applications that utilise mesophilic fermentations. / South Africa

Arbuscular mycorrhizal fungi (AMF) form a mutually beneficial symbiotic relationship with a majority of land plants through an exchange of nutrients. Despite the importance of AM symbiosis in agricultural and ecological settings, relatively little is known about how the fungal symbiont actively promotes symbiosis. To overcome a host’s immune response, plant pathogens secrete effector proteins that modify a host to suppress an immune response. Few effectors have been identified in AMF, as bioinformatics methods have failed to accurately predict their sequences. To successfully colonize a plant, AMF form structures called arbuscules within plant root cortical cells. Arbuscules are a primary site of nutrient exchange during AMF symbiosis. This work is built on the hypothesis that AMF produce effector proteins to promote symbiosis, and that arbuscules are a site of effector secretion. Using Rhizophagus irregularis, Glomus versiforme and Medicago truncatula this work applies a proteomics-based approach using a new biotechnology to identify fungal proteins secreted by AMF. This novel approach using proteomics and proximity labelling to identify proteins by mass spectrometry is the first time this system has been used to study the plant-AMF relationship. In this work, mass spectrometry identifies a total of 24 R. irregularis proteins and two G. versiforme proteins that are candidate effectors involved in the plant-AMF symbiosis.

Due to the increased occurrence of flooding, biological by-products such as mycotoxins can cause serious health problems for homeowners. This study used two species of fungi, Aspergillus fumigatus and Stachybotrys chartarum, which have been found within homes after flooding events. Two distinct types of mycotoxins can be produced; gliotoxin by A. fumigatus and trichothecenes by S. chartarum. A preliminary study evaluated four wall materials separately, for mycotoxin production and validation of techniques. Based on these results, the experimental study built replicated interior walls of gypsum wallboard, fiberglass batt insulation, wood stud, and oriented strand board; placed the walls in mold chambers on concrete pavers; flooded and drained the walls; and exposed these walls to S. chartarum for 65 days. All four building materials showed some level of mycotoxin present on all collection days. Gypsum wallboard and fiberglass batt insulation had the highest levels of trichothecenes and levels increased over time. The wood stud and oriented strand board also contained mycotoxins, but levels did not change over time. DNA concentrations were significantly higher on the batt insulation compared to wood products. However, DNA concentrations did not directly correlate to mycotoxin levels. These results support the removal of the batt insulation and gypsum wallboard from a home if a flooding event should occur. The finding of the mycotoxin on the wood products requires further research to better understand the mycotoxin’s properties on wood in order to ensure the safety of homeowners.

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The cultivated snapdragon ( Antirrhinum majus 3 .) is a perennial or biennial under culture, it is a member of the family Scrophulariaceae. The plant was introduced here from Europe. As an escape from gardens, it is rare in New England. The snapdragon has been a popular garden flower for two hundred years, but it is only within the last ten years that it has been grown to any extent as a greenhouse crop. There has been an increasing demand for it as a cut flower, and consequently an increasing amount of glass has been devoted to its culture. As a florist's crop, the snapdragon may be classed as about equal in importance to mignonette, schizanthus, stocks, pansies, and primulas (Nehrling, 1914), varying, of course, in different localities.

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