Promotion of Peptides Production of Solid-State Fermented Soybean Meal by Ultrasound-Enhanced Bacillus Amyloliquefaciens: Optimization of Ultrasound Conditions and Scale-up Test

Abstract

The aims of this study were to elucidate the influence of treating inoculum of Bacillus amyloliquefaciens (B. amyloliquefaciens) by ultrasound under different modes on peptides production in solid-state fermented soybean meal, and detect the validity of ultrasound enhancement effect in mass production through scale-up test. Results showed that the optimized ultrasound mode and parameters were as follows: simultaneous dual-frequency mode, 40 and 60 kHz, 40 W/L, 20 min, and pulse-on/off time of 40/60 s. Under these conditions, peptides content in fermented soybean meal came up to 154.28 mg/g. The value raised by 15.80% compared to the control. Among multi-frequency modes, simultaneous mode was superior to sequential mode, and tri-frequency mode was inferior to dual-frequency mode. Ultrasound enhancement accelerates the growth speed of B. amyloliquefaciens. This was helpful for promoting the bacterial proliferation and protease release during the preliminary stage, and consequently raising peptides production. The scale-up test demonstrated that effects of promoting peptides production in fermented soybean meal by treating the inoculum of B. amyloliquefaciens through ultrasound enhancement was valid. Peptides production increased by 12.40% compared to the control. Besides, the quality, safety, and bioactivity evaluation of fermented soybean meal in scale-up test pointed that ultrasound enhancement on inoculum would not downgrade the quality and safety of fermented soybean meal, and the treatment would improve the antioxidant activity of it. In brief, peptides production in fermented soybean meal could be prominently raised by ultrasound-enhanced inoculum of B. amyloliquefaciens. The effect was testified valid through scale-up test.