Objective  Fermentation processes utilizing soymilk processing wastewater to prepare feed additives with a high viable bacteria count and desirable functionalities were tested for applications.

  Method   Bacillus subtilis SB13 and B. licheniformis BL14 were cultured in the wastewater. Medium formulation and process optimization were conducted with a single factor experiment determined by the count of viable bacteria in the resulting preparations. Functions as an additive for chicken, pig, and cattle feeds of the preparations was evaluated by an in vitro simulated digestion and a DNS method.

  Result  Both SB13 and BL14 grew normally in the soymilk wastewater. The optimized culture processes for SB13 and BL14 included sporulation temperatures at 35 ℃ for 72 h and 48 h, respectively. To facilitate dehydrating the fermentation broths, a protective agent of 10% skim milk powder was added in the medium for SB13 and 4% sucrose for BL14, as well as a carrier of 10% wheat bran for SB13 and 10% starch for BL14. After completion of the fermentation, the broths were freeze-dried and kept in sealed containers prior to functionality tests. The dried SB13 agent showed a viable bacteria count of 6.40×10⁸ cfu·mL⁻¹ and a survival rate at 97.71%, while BL14 a count of 9.80×10⁸ cfu·mL⁻¹ and a survival rate at 94.69%. Upon the artificial gastric juice and pancreatic juice treatments for 2 h, the two preparations had survived counts ranged from 2.55×10⁷ to 13.10×10⁷ cfu·mL⁻¹. The endoglucanase activity of the preparations was more than 39% retained after the gastric juice treatment and 72% after the pancreatic juice treatment. Both agents displayed significant glycation on feed, and BL14 exhibited a significant inhibitory effect on Staphylococcus aureus.

  Conclusion   Utilizing the wastewater from soymilk processing to culture B. subtilis SB13 and B. licheniformis BL14 resulted in preparations that could become a functional additive to forages for livestock and poultry industry. The process was cost effective and environmentally friendly.