High-Protein Solid-State Symbiotic Fermentation of Sauce Residue for Probiotic Feed

The abuse of antibiotics in animal feed has caused a series of problems in livestock breeding, meat products and the natural environment. In this study, sauce residue was used as the main raw material that includes 25.98% of dry-based crude protein, 3.91% of NaCl, 16.28% of crude fat, 11.06% of the ash and the multi-strain solid-state symbiotic fermentation technology was used to increase the amount of probiotics and the crude protein content of feed. Meanwhile, the addition of functional probiotics improved the feed palatability, while reducing the use of antibiotics further improved the cycle utilization of soy sauce residue. This study systematically optimized the symbiotic conditions of two probiotics, Lactobacillus bulgaricus and Saccharomyces cerevisiae. This study defined viable cell count and crude protein content as the core targets for analysis and evaluation. Firstly, the optimal carbon source concentration, the temperature and the inoculation process of symbiotic fermentation were determined by single factors; then the symbiotic fermentation conditions (inoculation volume, material-liquid ratio, fermentation time) were optimized by orthogonal test. The results showed that 40 g/L glucose/lactose (50/50%) was the best carbon source for sauce residue fermentation. The optimum fermentation conditions were a ratio of material to water of 1:0.8 and an inoculation volume of 15% (v/w) and a fermentation duration of 48 h. Meanwhile, the study found that multi-step temperature control could effectively improve the corresponding targets. The inoculation with Saccharomyces cerevisiae first and then with Lactobacillus bulgaricus after 24 h, boosted the probiotic quantity and protein content. In optimized conditions, probiotic viable count reached 7.2×108 CFU·mL-1 and the crude protein content increased from 25.98% (dry content) to 38.86%, which is 49.6% increase compared with the raw material. This research could provide a reference for the development of high-protein probiotic feed using sauce residue.