The 53-kDa proteolytic product of precursor starch-hydrolyzing enzyme of Aspergillus niger has Taka-amylase-like activity

Changes in morphogenesis and carotenogenesis to influence polygalacturonase secretion in Aspergillus carbonarius mutant

Mycelial morphogenesis and the production of fungal secretory proteins are still largely unknown. A mutant strain of Aspergillus carbonarius UV-10046 produced abundant polygalacturonase (PG) along with partially saturated canthaxanthin (PSC) at low pH conditions. In the present study, the relationship between PG secretion and PSC biosynthesis was studied using carotenogenic inhibitors and SDS-PAGE electrophoresis. Also the correlation between morphogenesis and PG secretion was investigated by analysing through microscopic studies. From the results, it was observed that secretion of PG was positively influenced by the PSC biosynthesis. The results also showed that the mutant with hairy mycelial structure resulted in higher PG activity when compared to the wild type that lacks hyper branching. From the results, it was confirmed that a mutation might have occurred in the isoprenoid pathway that has helped mutant for survival at acidic conditions. Further, an alteration in the morphogenesis and hyper branching development caused over secretion of PG enzyme in the mutant.

Aspergillus Oryzae S2 α-Amylase Domain C Involvement in Activity and Specificity: In Vivo Proteolysis, Molecular and Docking Studies

We previously reported that Aspergillus oryzae strain S2 had produced two α-amylase isoforms named AmyA and AmyB. The apparent molecular masses revealed by SDS-PAGE were 50 and 42 kDa, respectively. Yet AmyB has a higher catalytic efficiency. Based on a monitoring study of the α-amylase production in both the presence and absence of different protease inhibitors, a chymotrypsin proteolysis process was detected in vivo generating AmyB. A. oryzae S2 α-amylase gene was amplified, cloned and sequenced. The sequence analysis revealed nine exons, eight introns and an encoding open reading frame of 1500 bp corresponding to AmyA isoform. The amino-acid sequence analysis revealed aY371 potential chymotrypsin cleaving site, likely to be the AmyB C-Terminal end and two other potential sites at Y359, and F379. A zymogram with a high acrylamide concentration was used. It highlighted two other closed apparent molecular mass α-amylases termed AmyB1 and AmyB2 reaching40 kDa and 43 kDa. These isoforms could be possibly generated fromY359, and F379secondary cut, respectively. The molecular modeling study showed that AmyB preserved the (β/α)8 barrel domain and the domain B but lacked the C-terminal domain C. The contact map analysis and the docking studies strongly suggested a higher activity and substrate binding affinity for AmyB than AmyA which was previously experimentally exhibited. This could be explained by the easy catalytic cleft accessibility.

Aspergillus oryzae S2 alpha-amylase production under solid state fermentation: optimization of culture conditions

Aspergillus oryzae S2 was assayed for alpha-amylase production under solid state fermentation (SSF). In addition to AmyA and AmyB already produced in monitored submerged culture, the strain was noted to produce new AmyB oligomeric forms, in particular a dominant tetrameric form named AmyC. The latter was purified to homogeneity through fractional acetone precipitation and size exclusion chromatography. SDS-PAGE and native PAGE analyses revealed that, purified AmyC was an approximately 172 kDa tetramer of four 42 kDa subunits. AmyC was also noted to display the same NH2-terminal amino acid sequence residues and approximately the same physico-chemical properties of AmyA and AmyB, to exhibit maximum activity at pH 5.6 and 60 °C, and to produce maltose and maltotriose as major starch hydrolysis end-products. Soyabean meal was the best substitute to yeast extract compared to fish powder waste and wheat gluten waste. AmyC production was optimized under SSF using statistical design methodology. Moisture content of 76.25%, C/N substrate ratio of 0.62, and inoculum size of 10(6.87) spores allowed maximum activity of 22118.34 U/g of dried substrate, which was 33 times higher than the one obtained before the application of the central composite design (CCD).