6 research outputs found
Enrichment of maize and triticale bran with recombinant Aspergillus tubingensis ferulic acid esterase
Ferulic acid is a natural antioxidant found in
various plants and serves as a precursor for various fine
chemicals, including the flavouring agent vanillin. However,
expensive extraction methods have limited the commercial
application of ferulic acid, in particular for the
enrichment of food substrates. A recombinant Aspergillus
tubingensis ferulic acid esterase Type A (FAEA) was
expressed in Aspergillus niger D15#26 and purified with
anion-exchange chromatography (3487 U/mg, Km =
0.43 mM, Kcat = 0.48/min on methyl ferulate). The
36-kDa AtFAEA protein showed maximum ferulic acid
esterase activity at 50 C and pH 6, suggesting potential
application in industrial processes. A crude AtFAEA
preparation extracted 26.56 and 8.86 mg/g ferulic acid
from maize bran and triticale bran, respectively, and also
significantly increased the levels of p-coumaric and caffeic
acid from triticale bran. The cost-effective production of
AtFAEA could therefore allow for the enrichment of brans
generally used as food and fodder, or for the production of
fine chemicals (such as ferulic and p-coumaric acid) from
plant substrates. The potential for larger-scale production
of AtFAEA was demonstrated with the A. niger D15[AtfaeA]
strain yielding a higher enzyme activity (185.14 vs.83.48 U/ml) and volumetric productivity (3.86 vs. 1.74 U/ml/h) in fed-batch than batch fermentation.In part by the National Research Foundation of
South Africa (Grant 76597 to MVB and Grant 86423 to WHvZ).http://link.springer.com/journal/131972018-03-31hb2017Food Scienc
Raw starch conversion by Saccharomyces cerevisiae expressing Aspergillus tubingensis amylases
Publication of this article was funded by the Stellenbosch University Open Access Fund.The original publication is available at :Viktor, M. J., Rose, S. H., Van Zyl, W. H. & Viljoen-Bloom, M. 2013. Raw starch conversion by Saccharomyces cerevisiae expressing Aspergillus tubingensis amylases. Biotechnology for Biofuels, 6:167, doi:10.1186/1754-6834-6-167.The original publication is available at http://www.biotechnologyforbiofuels.com/Background: 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.Stellenbosch UniversityPublishers' Versio
Comparative secretome analysis of Trichoderma asperellum S4F8 and Trichoderma reesei Rut C30 during solid-state fermentation on sugarcane bagasse
Publication of this article was funded by the Stellenbosch University Open Access Fund.The original publication is available at :Marx, I. J. et al. 2013. Comparative secretome analysis of Trichoderma asperellum S4F8 and Trichoderma reesei Rut C30 during solid-state fermentation on sugarcane bagasse. Biotechnology for biofuels, 6:172, doi:10.1186/1754-6834-6-172.The original publication is available at http://www.biotechnologyforbiofuels.com/Background: 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.Stellenbosch UniversityPublishers' Versio
Additional glucoamylase genes increase ethanol productivity on rice and potato waste streams by a recombinant amylolytic yeast
: The implementation of consolidated bioprocessing for converting starch to ethanol relies on a robust yeast that produces enough amylases for rapid starch hydrolysis. Furthermore, using low-cost substrates will assist with competitive ethanol prices and support a bioeconomy, especially in developing countries. This paper addresses both challenges with the expression of additional glucoamylase gene copies in an efficient amylolytic strain (Saccharomyces cerevisiae ER T12) derived from the industrial yeast, Ethanol Red™. Recombinant ER T12 was used as a host to increase ethanol productivity during raw starch fermentation; the ER T12.7 variant, selected from various transformants, displayed enhanced raw starch conversion and a 36% higher ethanol concentration than the parental strain after 120 h. Unripe rice, rice bran, potato waste and potato peels were evaluated as alternative starchy substrates to test ER T12.7's fermenting ability. ER T12.7 produced high ethanol yields at significantly improved ethanol productivity, key criteria for its industrial application