Production Of Protein Feed And Lactic Acid Bacteria Probiotic Feed Additive By Solid-state Fermentation Of Corn Starch Sugar Residue

Corn starch sugar residue（CSSR）is a by-product of corn starch liquefaction and saccharification,rich in reducing sugar,protein and dietary fiber.However,CSSR has low feeding efficiency as feed raw material due to its poor palatability and nutritional limitations.This paper aims to achieve the high-value utilization of CSSR,improve its palatability and degrade the nutritional limiting factors.A microbial solid-state fermentation method was adopted,in which Saccharomyces cerevisiae was used to ferment the CSSR and convert the reducing sugar into yeast protein,and then Bacillus subtilis was added to degrade the corn protein into free amino acids to produce protein feed.Meanwhile,Bacillus subtilis and Lactobacillus acidophilus were used synergistically to ferment the CSSR and produce a Lactic acid bacteria feed additive with high viable count.（1）The protein content of sugar residue was enhanced by solid-state fermentation with Saccharomyces cerevisiae.The optimal conditions were 5.26%bran,55%moisture,5%inoculum,initial p H 7,air humidity 70%,and temperature 30°C for 48 h,resulting in 4.21×10⁹CFU·g^-1 of yeast and 51.96%of protein,which was 1.30 times higher than that of sugar residue.Furthermore,the addition of Bacillus subtilis was optimized.The free amino acid content reached 7.20 mg·g^-1,which was 4.14 times higher than that of the control,when 0.5%Bacillus subtilis was added at 24 h.（2）The production of Lactobacillus acidophilus feed additive with high viable count by solid-state fermentation of sugar residue was optimized.The optimal conditions were 5:2 ratio of Lactobacillus acidophilus and Bacillus subtilis dual inoculum,7.8%inoculation amount,72%moisture content,initial p H 7.26,20 g loading amount of 250 m L triangular flask,and 37°C fermentation temperature for 48 h.Under these conditions,the viable count of Lactobacillus acidophilus was 5.05×10⁹ CFU·g^-1,which was 3.37 times higher than the unoptimized level.（3）The fermentation products of Saccharomyces cerevisiae,the co-fermentation products of Saccharomyces cerevisiae and Bacillus subtilis,the fermentation products of Lactobacillus acidophilus and the co-fermentation products of Lactobacillus acidophilus and Bacillus subtilis were analyzed and compared with the unfermented CSSR.The results showed that the total phenolic content and antioxidant capacity of the four fermentation products were increased,while the phytic acid content was decreased,indicating that the functionality of the fermentation products was significantly enhanced.Based on the sensory analysis provided by electronic nose,electronic tongue and free amino acids of flavor,the results showed that the taste and flavor of the four fermentation products were significantly different from those of the unfermented sugar residue.The co-fermentation product of Saccharomyces cerevisiae and Bacillus subtilis enhanced the bitterness and umami sweetness,while the co-fermentation product of Lactobacillus acidophilus and Bacillus subtilis weakened the bitterness and sweetness,and increased the umami and sourness.In terms of flavor,the unpleasant odor of CSSR such as sourness was reduced after fermentation.The fermentation product of Saccharomyces cerevisiae increased the fruity sweet flavor and slight alcohol aroma,while the co-fermentation product of Saccharomyces cerevisiae and Bacillus subtilis had stronger sweet flavor than that of Saccharomyces cerevisiae.The fermentation product of Lactobacillus acidophilus increased the ester-like aroma,while the co-fermentation product of Lactobacillus acidophilus and Bacillus subtilis added a nut-like flavor.The flavor of the fermentation products was improved after fermentation.