Corn Steep Liquor (CSL) is wastewater from corn starch industry. The huge amount generation made it as a serious environmental problem. But CSL is nutrient-rich with diverse amino acids and other trace elements. In this study, symbiotic biofertilizer was studied using CSL as main substrate. In this study, 9 industrial strains, which were recognized as high performance species in the biofertilizer industry were collected, including four bacillus, four fungus and one yeast species. Three dominant strains were selected finally, depending on the ability to dissolve phosphorus, ability for protein hydrolysis and cell growth. They were Bacillus subtilis 3301, Bacillus licheniformis and Aspergillus Niger. The results expressed that the highest growth cell count of Bacillus subtilis 3301 reached 3.1×10 9 CFU/mL, the highest protein hydrolysis capacity of Bacillus licheniformis reached 600 mg/L and the highest phosphorus-dissolving capacity of Aspergillus Niger reached 1100 mg/L respectively. Then, symbiotic fermentation of the three strains was carried out both in shake-flask culture and fermentation tank (5 L). Interestingly, series of significant data of symbiotic fermentation were obtained, which were different from individual cultures. Especially, the total growth cell count in the 5 L scale fermenter culture was higher than individual cultures, which proved the mutual promotion effect between different strains. This research would provide a new view to utilize the waste of corn steep liquor as high value-added agricultural products.
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 multistep 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 7.2×10 8 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.
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