Browsing by Author "Viljoen-Bloom, Marinda"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- ItemComparative secretome analysis of Trichoderma asperellum S4F8 and Trichoderma reesei Rut C30 during solid-state fermentation on sugarcane bagasse(BioMed Central, 2013-11) Marx, Isa Jacoba; Van Wyk, Niel; Smit, Salome; Jacobson, Daniel; Viljoen-Bloom, Marinda; Volschenk, HeinrichBackground: The lignocellulosic enzymes of Trichoderma species have received particular attention with regard to biomass conversion to biofuels, but the production cost of these enzymes remains a significant hurdle for their commercial application. In this study, we quantitatively compared the lignocellulolytic enzyme profile of a newly isolated Trichoderma asperellum S4F8 strain with that of Trichoderma reesei Rut C30, cultured on sugarcane bagasse (SCB) using solid-state fermentation (SSF). Results: Comparison of the lignocellulolytic enzyme profiles of S4F8 and Rut C30 showed that S4F8 had significantly higher hemicellulase and β-glucosidase enzyme activities. Liquid chromatography tandem mass spectrometry analysis of the two fungal secretomes enabled the detection of 815 proteins in total, with 418 and 397 proteins being specific for S4F8 and Rut C30, respectively, and 174 proteins being common to both strains. In-depth analysis of the associated biological functions and the representation of glycoside hydrolase family members within the two secretomes indicated that the S4F8 secretome contained a higher diversity of main and side chain hemicellulases and β-glucosidases, and an increased abundance of some of these proteins compared with the Rut C30 secretome. Conclusions: In SCB SSF, T. asperellum S4F8 produced a more complex lignocellulolytic cocktail, with enhanced hemicellulose and cellobiose hydrolysis potential, compared with T. reesei Rut C30. This bodes well for the development of a more cost-effective and efficient lignocellulolytic enzyme cocktail from T. asperellum for lignocellulosic feedstock hydrolysis.
- ItemRaw starch conversion by Saccharomyces cerevisiae expressing Aspergillus tubingensis amylases(BioMed Central, 2013-11) Viktor, Marko J.; Rose, Shaunita H.; Van Zyl, Willem H.; Viljoen-Bloom, MarindaBackground: Starch is one of the most abundant organic polysaccharides available for the production of bio-ethanol as an alternative transport fuel. Cost-effective utilisation of starch requires consolidated bioprocessing (CBP) where a single microorganism can produce the enzymes required for hydrolysis of starch, and also convert the glucose monomers to ethanol. Results: The Aspergillus tubingensis T8.4 α-amylase (amyA) and glucoamylase (glaA) genes were cloned and expressed in the laboratory strain Saccharomyces cerevisiae Y294 and the semi-industrial strain, S. cerevisiae Mnuα1. The recombinant AmyA and GlaA displayed protein sizes of 110–150 kDa and 90 kDa, respectively, suggesting significant glycosylation in S. cerevisiae. The Mnuα1[AmyA-GlaA] and Y294[AmyA-GlaA] strains were able to utilise 20 g l⁻¹ raw corn starch as sole carbohydrate source, with ethanol titers of 9.03 and 6.67 g l⁻¹ (0.038 and 0.028 g l⁻¹ h⁻¹), respectively, after 10 days. With a substrate load of 200 g l⁻¹ raw corn starch, Mnuα1[AmyA-GlaA] yielded 70.07 g l⁻¹ ethanol (0.58 g l⁻¹ h⁻¹) after 120 h of fermentation, whereas Y294[AmyA-GlaA] was less efficient at 43.33 g l-1 ethanol (0.36 g l⁻¹ h⁻¹). Conclusions: In a semi-industrial amylolytic S. cerevisiae strain expressing the A. tubingensis α-amylase and glucoamylase genes, 200 g l⁻¹ raw starch was completely hydrolysed (saccharified) in 120 hours with 74% converted to released sugars plus fermentation products and the remainder presumably to biomass. The single-step conversion of raw starch represents significant progress towards the realisation of CBP without the need for any heat pretreatment. Furthermore, the amylases were produced and secreted by the host strain, thus circumventing the need for exogenous amylases.