| With the increase of energy demand and the depletion of oil resources,it is necessary to seek alternative energy.After hydrolyzing kitchen waste into reducing sugar,the production of fuel ethanol by fermentation is an important direction of bioenergy.The production of fuel ethanol from kitchen waste can not only be used as a resource,but also increase the energy supply to eliminate its harm to the environment.Among them,rich in starch,cellulose,protein and other organic substances,rich in nutrients,biodegradable,it has become the focus of research on resource treatment.The technology of anaerobic microbial fermentation to produce ethanol from kitchen waste has high efficiency.Because it has the advantages of high organic load bearing capacity and simple process,it is more important to recycle biomass energy at the same time of disposal of waste and kitchen waste.It can be predicted that the production of ethanol from microbial fermented kitchen waste is the main direction of large-scale treatment of kitchen waste in the future.In this study,the cellulose decomposing bacteria stored in the laboratory and ethanol bacteria were used for ethanol fermentation.By comparing the ethanol concentration under different fermentation modes,the optimal ethanol fermentation technology was obtained to provide the basic data for optimizing the ethanol fermentation of kitchen waste.In order to reduce the environmental pollution of kitchen waste,good economic benefits have been achieved.At the same time,the microbial diversity in ethanol fermentation process was explored,and the microbial action mechanism of food waste ethanol fermentation was preliminarily clarified from the point of view of microbial ecology.The findings are as follows:(1)In the stem and leaf of vegetable,the best way of co-fermentation culture wasas follows: adding ethanol bacteria first under the condition of not sterilizing,adding cellulose decomposing bacteria after 6 hours(fermentation mode 6),the highest ethanol concentration was 0.57%(v/v),and the highest concentration of ethanol was0.57%(v/v).The highest concentration of lactic acid was 5.64 g / L,The yield of p H was inversely proportional to that of lactic alcohol,and the yield of lactic acid was proportional to that of ethanol.(2)In the meat,the best way to produce lactic acid in the co-fermentation is to add the cellulose to decompose the flora under the condition of non-sterilization,add the ethanol group after 6 h(fermentation mode 3),the lactic acid concentration is up to 58.38 g/ L,and the p H and the lactic acid yield are independent.(3)In the kitchen waste,the optimal co-culture mode of ethanol production was as follows: adding cellulose decomposition bacteria first under sterile condition,adding ethanol bacteria(fermentation mode 3)after 6 hours,the highest ethanol concentration reaches 3.25%(v/v),and the concentration of lactic acid reaches37.77g/L;the best co-culture fermentation mode for ethanol production is adding cellulose decomposition bacteria first under sterile condition,and adding ethanol bacteria after 12 hours.(fermentation mode 2),ethanol concentration reached 2.90%(v/v),lactic acid concentration reached the highest value of 57.24 g/L,The yield of p H was inversely proportional to that of lactic alcohol,and the yield of lactic acid was proportional to that of ethanol.(4)The microbial diversity of fermented samples pretreated with sterilization,sterilization and T160 was sequenced by 16 Sr DNA.The results showed that the diversity of fermented bacteria was very rich in the three fermentation modes,and their community structure was similar.At the taxonomic level,the phylum mainly includes Firmicutes,Proteobacteria,Bacteroidetes,Cyanobacteria,Actinobacteria and Synergistetes,among which Firmicutes and Proteobacteria are the dominant phylum.The relative abundance is over 90%.Based on the alpha diversity index of three fermentation modes,there is no significant difference between the fermentation bacteria of non-sterilized kitchen waste and that of sterilized kitchen waste,but there is significant difference between the fermentation bacteria of non-sterilized kitchenwaste and that of pre-treated kitchen waste under T160.At the same time,the diversity of fermentation bacteria of sterilized kitchen waste was slightly higher than that of non-sterilized kitchen waste,and both diversity was higher than that of fermentation bacteria of kitchen waste under T160 condition.(5)Under sterilized conditions,there was a weak negative correlation between the yield of ethanol and lactic acid and shannon index,and between shannon index and p H index.There was a weak negative correlation trend between microbial diversity and the yield of ethanol and lactic acid,and a weak positive correlation trend between microbial diversity and the yield of ethanol and lactic acid,and between the microbial diversity and the yield of ethanol and lactic acid.The correlation between unsterilized and sterilized condition was similar to that under sterilized condition.It is worth noting that ethanol yield and lactic acid yield have significant weak positive correlation with ace(that is,significant weak positive correlation with microbial quantity).This is a different trend from sterilization.(6)As the condition of affecting microbial diversity,the pretreatment of meal waste had a great effect on(Pediococcus),and had a higher content when the food waste was not treated with high temperature.The(Lactobacillus)content of lactic acid bacteria was higher after high temperature sterilization of kitchen waste.The(Lactobacillus)content of Lactobacillus was higher than that of sterilization at T160.(7)The community structure of fungi in the fermentation samples of seven days under the three pretreatment conditions was similar.At the classification level of the phylum,it mainly includes Ascomyces(Ascomycota),and(Zygomycota),basidiomycetes(Basidiomycota).Ascomycetes are absolutely dominant,and the relative abundance is more than 94%.Based on the α diversity index,it was found that there was no significant difference in fungal diversity among the three pretreatment fermentation methods.Fungal diversity T160 > unsterilized > sterilized.At the classification level of the genus,it mainly includes the genus Saccharo(Saccharomyces cerevisiae).Aspergillus myces),(Aspergillus),(Rhizopus),candida(Candida),Saccharomyces(Kazachstania),.The content of Saccharomyces was higher under sterilization condition and T160 pretreatment condition,and the content ofSaccharomyces was higher than that of Saccharomyces cerevisiae under sterilization condition and T160 pretreatment condition.The content of candida is higher under the condition of non-sterilization.(8)There was a significant positive correlation between species abundance and ethanol and lactic acid yield under sterilization conditions.Fungal diversity was negatively correlated with p H and positively correlated with ethanol and lactic acid production.Under the condition of no sterilization,there was a significant positive correlation between species abundance and p H,but a weak correlation with the yield of ethanol and lactic acid.Fungal diversity was positively correlated with p H and negatively correlated with lactic acid yield. |
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