Pilot-Scale Study On Biogas Production From Molasses And Analysis Of Microbial Community Structure During Fermentation

Molasses is a by-product produced in the process of pressing sugar.It is a viscous,high-color and semi-fluidity substance.Its main component is sucrose,but also contains a small amount of protein and minerals.50-60%molasses are mainly used to produce alcohol,and the rest can be used to produce feed,aquaculture,crop fertilizer and biological products,but the utilization rate is low.The main purpose of this experiment is to produce biogas by anaerobic fermentation of molasses.By adjusting the fermentation process,the fermentation efficiency and biogas production can be improved,which provides the basis for large-scale anaerobic fermentation of molasses to produce biogas.IC anaerobic fermentation reactor was used in this experiment,anaerobic activated sludge and pig manure were used as inoculated sludge,molasses were used as fermentation raw materials for anaerobic fermentation,in which the volume ratio of activated sludge,pig manure and molasses water was 3:1:6,and the effective volume of fermentation was 2 m3.The initial hydraulic load is 1250 mg COD/(L d).After the domestication period,the hydraulic load is increased to 2500 mg COD/(L d).The COD removal rate and gas production of molasses are recorded and adjusted.The maximum removal rate of COD is about 87.6%and the maximum biogas production is 2.36 m3 per day after the influent load is adjusted to 2000 mg COD/(L d),the influent mode is changed to intermittent sampling mode and the external circulation device is installed.In this experiment,10 sludge samples from different fermentation stages were collected and anaerobically cultured at 25,30 and 37?.After isolation and purification of the cultured strains,16S rDNA sequence of the strain was sequenced and identified.The sequencing results were compared with 16S rDNA in NCBI database.It was found that the species of microbial flora cultured at different temperatures were different,Enterococcus,Lactobacillus and Bacillus were the common bacterial flora at the three temperatures.The results showed that the three microflora had strong temperature adaptability.Clostridium is an important bacteria in anaerobic fermentation.It can decompose proteins and ferment sugars,some Clostridium can produce acid and gas.But it did not appear in the flora cultured at 25?.It shows that Clostridium is sensitive to temperature and can not grow at low temperature(25?).High throughput sequencing of sludge samples from different fermentation stages was carried out to analyze the composition of microbial community structure.The OTU numbers of bacteria were 522,529,532,528,536,557,586,583,567,568 and 622,and the OTU numbers of archaea were 96,95,93,90,97,107,108,107,106 and 110,respectively.The species of bacteria in 10 samples were basically the same at the phylum level,mainly Chloroflexi,Actinobacteria,Bacteroidetes,Saccharibacteria,Firmicutes,Proteobacteria and Synergistetes,but the species abundance changed at different fermentation stages.