| Distiller’s grains is the main by-product in the production process of Baijiu.It contains rich nutrients such as crude protein,crude fat and amino acids,and is widely used in producing feed,organic fertilizer,chemical products,etc.Among of them,the feed research of distiller’s grains is beneficial to solve the problem of the lack of feed protein resources in my country,so as to realize the green production and rational use of resources in the Baijiu industry.In this study,the optimized steam explosion conditions were used to pretreat distiller’s grains,and the best combination of strains determined through experiments was used to ferment it.And then,the fermentation conditions were optimized through single factor experiments combined with orthogonal experiments and response surface experiments,so as to produce distiller’s grains feed rich in functional substances through microbial mixed fermentation.(1)Taking the content of lignin,hemicellulose and reducing sugar as detection indexes.The influence of steam explosion pressure and steam explosion time on steam explosion of distiller’s grains were explored.The optimal pretreatment conditions for steam explosion of distiller’s grains were determined as follows: steam explosion pressure 1.7 MP,steam explosion time 15 min.(2)Three strains of lactic acid bacteria were combined with Saccharomyces cerevisiae,Candida utilis,Bacillus subtilis and Trichoderma koningii to ferment distiller’s grains respectively.According to the content of short chain organic acids and the diameter of inhibition zone in the three groups of experiments,Lactobacillus plantarum was selected as feeding lactic acid bacteria.Then the four strains of fungi were randomly combined with fixed strains(S.cerevisiae,C.utilis,L.plantarum,B.subtilis)to ferment distiller’s grains.Comparing the production of various functional substances and degrading crude fiber by fermenting distiller’s grains with different combinations of strains,the best combination of strains was determined as: S.cerevisiae,C.utilis,L.plantarum,B.subtilis,T.koningii,Aspergillus niger H7,A.niger H1496 and Myceliophthora thermophile.(3)Through single factor experiment,the optimal strain combination fermentation conditions for fermented distiller’s grains to produce feed were optimized.The optimal conditions were as follows: bran addition 10%,loading 100 g,initial p H 4.67,fermentation time 5 d,fermentation temperature 30 ℃ and inoculum 10%.Based on single factor experiment,orthogonal experiment and response surface experiment were designed to optimize the medium conditions and fermentation conditions,respectively.The optimal conditions were determined as follows: bran addition 5%,loading 80 g,initial p H 3.70,fermentation time 3.91 d,fermentation temperature 32.35 ℃ and inoculum 15%.(4)The distiller’s grain feed produced under optimal conditions was comprehensively evaluated.The sensory evaluation of distiller’s grains fermented feed was conducted from three aspects of odor,texture and color.After comprehensive evaluation,the final score of distiller’s grains feed under the optimized conditions was 17 points,which was excellent(grade 1)fermented feed.Under this condition,the content of crude protein and crude fiber in distiller’s grains feed was 36.51% and 11.29%,respectively,the content of nicotinic acid in distiller’s grains was 2.04 mg/g,and the content of acetoin was 29.25 mg/g.At the same time,its rumen digestibility and intestinal digestibility in vitro are better than those of unfermented distillers grains and distillers grain feed before optimize.The digestibility of crude protein in rumen,dry matter in rumen,crude protein in intestine and dry matter in intestine were 38.57%,32.51%,13.24%and 15.80%,respectively.In addition,the optimized distiller’s grain feed extract has much better inhibitory effect on pathogenic indicator bacteria(Escherichia coli)than the unfermented distiller’s grain extract. |
