Characterization and application of Bacillus velezensisD6 co‐producing α‐amylase and protease

Abstract

AbstractBACKGROUNDResearch on the co‐production of multiple enzymes by Bacillus velezensis as a novel species is still a topic that needs to be studied. This study aimed to investigate the fermentation characteristics of B. velezensis D6 co‐producing α‐amylase and protease and to explore their enzymatic properties and applications in fermentation.RESULTSThe maximum co‐production of α‐amylase and protease reached 13.13 ± 0.72 and 2106.63 ± 64.42 U mL−1, respectively, under the optimal fermented conditions (nutrients: 20.0 g L−1 urea, 20.0 g L−1 glucose, 0.7 g L−1 MnCl2; incubation conditions: initial pH 7.0, temperature 41 °C, 8% inoculation size and 30% working volume). Moreover, the genetic co‐expression of α‐amylase and protease increased from 0 to 24 h and then decreased after 36 h at the transcriptional level, which coincided with the growth trend of B. velezensis D6. The optimal reaction temperature of α‐amylase was 55–60 °C, while that of protease was 35–40 °C. The activities of α‐amylase and protease were retained by over 80% after thermal treatment (90 °C, 1 h), which indicated that two enzymes co‐produced by B. velezensis D6 demonstrated excellent thermal stability. Moreover, the two enzymes were stable over a wide pH range (pH 4.0–8.0 for α‐amylase; pH 4.0–9.0 for protease). Finally, the degrees of hydrolysis of corn, rice, sorghum and soybeans by α‐amylase from B. velezensis D6 reached 44.95 ± 2.95%, 57.16 ± 2.75%, 52.53 ± 4.01% and 20.53 ± 2.42%, respectively, suggesting an excellent hydrolysis effect on starchy raw materials. The hydrolysis degrees of mackerel heads and soybeans by protease were 43.93 ± 2.19% and 26.38 ± 1.72%, respectively, which suggested that the protease from B. velezensis D6 preferentially hydrolyzed animal‐based protein.CONCLUSIONThis is a systematic study on the co‐production of α‐amylase and protease by B. velezensis D6, which is crucial in widening the understanding of this species co‐producing multi‐enzymes and in exploring its potential application. © 2024 Society of Chemical Industry.