Mingsheng Lv

Optimization of the production of organic solvent-stable protease by Bacillus sphaericus DS11 with response surface methodology

Response surface methodology (RSM) was employed to enhance the production of organic solvent-stable protease by Bacillus sphaericus DS11. A significant influence of glycerol, MgSO₄·7H₂O, and pH on organic solvent-stable protease production was noted with Plackett-Burman design. Then, a three-level Box-Behnken design was employed to optimize the medium composition and culture conditions for the production of the protease in shake-flask. Using this methodology, the quadratic regression model of producing organic solvent-stable protease was built and the optimal combinations of media constituents and culture conditions for maximum protease production were determined as glycerol 12.47 g/L, MgSO₄·7H₂O 0.73 g/L, and pH 8.25. Protease production obtained experimentally coincident with the predicted value and the model was proven to be adequate. The enhancement of protease from 465.06 U/mL to 1182.68 U/mL was achieved with the optimization procedure.

An evolutionary analysis of the GH57 amylopullulanases based on the DOMON_glucodextranase_like domains

Thermostable amylopullulanase (TAPU) is valuable in starch saccharification industry for its capability to catalyze both α‐1,4 and α‐1,6 glucosidic bonds under the industrial starch liquefication condition. The majority of TAPUs belong to glycoside hydrolase family 57 (GH57). In this study, we performed a phylogenetic analysis of GH57 amylopullulanase (APU) based on the highly conserved DOMON_glucodextranase_like (DDL) domain and classified APUs according to their multidomain architectures, phylogenetic analysis and enzymatic characters. This study revealed that amylopullulanase, pullulanase, andα‐amylase had passed through a long joint evolution process, in which DDL played an important role. The phylogenetic analysis of DDL domain showed that the GH57 APU is directly sharing a common ancestor with pullulanase, and the DDL domains in some species undergo evolution scenarios such as domain duplication and recombination.