| China is a big country in agricultural cultivation and agricultural production,in2017,the theoretical resources of straw were close to 1.09 billion tons,and about 200 million tons were not used,the utilization rate of straw resources needs to be improved.At the same time,China is also a major producer and consumer of white wine,the amount of distiller's grains produced each year is as high as 40 million tons,and its resources are abundant.These agricultural production wastes are also widely sourced biomass resources,the utilization of waste resources is an effective way to improve environmental pollution,develop a recycling economy,and achieve sustainable development of agricultural production.However,there is a structural contradiction between the seasonality and timeliness of crop straw harvesting and its sustainable use throughout the year,which will inevitably require straw to be stored for a long time,so as to meet the sustainable supply of raw materials in the process of waste resource utilization.In order to achieve long-term storage and resource utilization of crop straw and distiller's grains biomass feedstock,this article uses sweet sorghum stalks(G)and distiller's grains(J)as the experimental materials,using the principle of silage to carry out mixed solid-state fermentation,the mixed masse ratios of six gradients of 5:1,2:1,1:1,1:2,1:6,0:1 were set,respectively,the six treatment groups were named GJ.1,GJ.2,GJ.3,GJ.4,GJ.5 and GJ.6.After continuous solid state fermentation for 160 days,dynamic analysis of sensory quality,nutrient composition,lignocellulose composition,fermentation characteristics,number of major microorganisms,and microbial flora diversity was performed on 40,80,120,and 160 days,respectively.The research results mainly include the following aspects:(1)The results of sweet sorghum straw and distillers' grains showed that the water and soluble carbohydrate contents of sweet sorghum stalk were 5.25% and31.19%,respectively.The contents of water,starch and crude protein in distillers' grains were 60.34%,19.92%,and 12.91%,respectively.The two materials are mixed solid-state fermentation with the principle of silage,has good complementary properties.The results of sensory evaluation of solid-state fermentation showed that the sensory evaluation results of the four treatment groups of GJ.1,GJ.2,GJ.4 and GJ.5 were superior to those of GJ.3 and GJ.6 when fermentation for 80 d;the sensory evaluation results of the five treatment groups of GJ.1,GJ.2,GJ.3,GJ.4,and GJ.5were superior to that of the GJ.6 group when fermentation for 120 d.(2)The results of organic chemical components in solid-state fermentation indicated that the contents of starch and crude protein in the three treatment groups of GJ.4,GJ.5,and GJ.6 were significantly higher than those of GJ.1,GJ.2,and GJ.3,the GJ.6 group had a high crude protein content of 20.56% when fermentation for 160 d,and had a high starch content of 24.82% when fermentation for 80 d.The water-soluble carbohydrates in the three treatment groups of GJ.1,GJ.2,and GJ.3were significantly higher than those of GJ.4,GJ.5,and GJ.6,the water-soluble carbohydrate content in the GJ.1 group was 30.01% when fermentation for 0 d.The contents of neutral detergent fibers and acid detergent fibers in the three treatment groups of GJ.4,GJ.5 and GJ.6 were significantly lower than those of GJ.1,GJ.2,and GJ.3,and the hemicellulose content of the three treatment groups was well preserved.The results of fermentation characteristics showed that the pH values of the GJ.1 and GJ.2 exceeded the recommended pH range(pH<4.2)of the excellent silage during fermentation for 160 days,and the pH value of the GJ.3 group was higher than 4.2during fermentation for 160 days,but were all in the range of spoilage(pH>4.5),the pH values of the three treatment groups of GJ.4,GJ.5,and GJ.6 are always within the excellent silage,the lactic acid content of the three treatment groups were significantly higher than that of the other treatment groups.The ratio of ammonia nitrogen to total nitrogen and ethanol content of the six treatment groups of GJ.1,GJ.2,GJ.3,GJ.4,GJ.5 and GJ.6 increased with the proportion of distillers' grains in the fermentation system,the ratio of ammonia nitrogen to total nitrogen of the GJ.6 group exceeded the recommended value of excellent silage when fermentation for 40 d and120 d(10%).(3)Changes in the number of major microorganisms such as lactic acid bacteria,yeasts,and molds during the fermentation process indicate that the six treatment groups of GJ.1,GJ.2,GJ.3,GJ.4,GJ.5,and GJ.6 increase with the proportion of distiller's grains.The number of lactic acid bacteria colonies in the six treatment groups increased first and then decreased,while the number of yeast and mold colonies showed a decreasing trend.(4)Analysis of bacterial community diversity during solid-state fermentation using high-throughput sequencing technology showed that Proteobacteria or Firmicutes is the dominant bacteria at the level of the phylum in the six treatment groups of GJ.1,GJ.2,GJ.3,GJ.4,GJ.5,and GJ.6;Lactobacillus and Pediococcus are dominant bacteria at the level of the genus,the relative abundance of lactic acid bacteria in the three treatment groups of GJ.4,GJ.5,and GJ.6 was significantly higher than those of GJ.1,GJ.2 and GJ.3.(5)The result of fungal community diversity showed that Ascomycota in the six treatment groups of GJ.1,GJ.2,GJ.3,GJ.4,GJ.5 and GJ.6 were the dominant bacteria at the phylum level,the relative abundance of Ascomycota in the GJ.3 group was as high as 100% when fermentation for 40 d and 160 d,and as high as 100% in the GJ.4group when fermentation for 120 d and 160 d.Pichia,Candida,and Aspergillus are dominant bacteria at genus level,and the relative abundance of Monascus is as high as 99% in the GJ.3 group when fermentation for 160 d.Based on the above results,the fermentation quality in the three treatment groups of GJ.4,GJ.5 and GJ.6 were superior to those of GJ.1,GJ.2 and GJ.3.However,considering the combination of sensory quality,dry matter recovery,organic matter preservation,and relative abundance of lactic acid bacteria,when the mass ratio of sweet sorghum stalks to distiller's grains is 1:6,the effect of mixed solid state fermentation is relative best. |
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