| In recent years,black soldier flies have been widely concerned and applied in the resource utilization of agricultural organic waste such as food waste and livestock manure.The rich oils and fats in food waste could provide valuable nutrients for the growth of the larvae,but the excessively high oils and fats in the later breeding stage could bring negative impact on the large-scale farming of the black soldier flies.Stick oil will block the stigma of black soldier fly larvae,resulting in high mortality rate and could also seriously affects the separation of the larvae from feces.We isolated the functional intestinal bacteria from the larvae with the ability of oil-degrading and carried out preliminary application in treatment of food waste.The intestinal oildegrading bacteria could decompose the grease of the food waste,which could provide functional bacteria resources and could be applied in the resource utilization of the food waste by the black soldier flies.The main results of this paper are described as following:(1)We isolated a total of 8 oil-degrading bacteria strains from the gut of Hermetia illucens larvae and strain X8 was selected as high ability of grease degrading and could degrade 64.9% oil in 72 h.Strain X8 is a gram-negative bacteria and the colony is white with smooth surface,neat and rounded edges on LB plate.Based on the combination of morphological,physiological and biochemical properties and 16 S r DNA sequences,strain X8 was identified as Aeromonas veronii.(2)We optimized the conditions of growth and oil-degradation for strain X8.The optimum growth conditions could set as: inoculation rate 2%,37℃,and initial p H of7.0-8.0.Inorganic salt concentration was the main factor that affect the ability of oildegradation of X8.The oil-degrading activity decreased dramatically when the inorganic salt concentration reached 25 g/L or more.Under the optimal degradation conditions,the oil degradation rate of X8 strain reached 80.4% after 48 h,and the lipase activity reached 36.7 U/m L.(3)The whole genome sequences of X8 were determined and it was 4.54 Mb in total length,containing only one circular chromosome without plasmid.The GC content is 58.51%,and the whole genome contains 3984 protein-coding genes,123 t RNA and31 r RNA genes.We identified a lipase encoding gene Lip K(X8＿00285)and its modulator Lim K(X8＿00284)in the genome of strain X8 in the same operon.Lip K encodes a secretory lipase with 303 amino acids in length.Lip K contains a typical lid domain,which is essential for its activity at lipid-water interfaces.We also identified all the genes involving in glyoxylate cycle,which can allows cells to use two carbons(C2 compounds),such as acetate,to satisfy cellular carbon requirements when simple sugars such as glucose or fructose are not available.(4)Inoculating X8 broth could significantly improve the survival rate of black soldier fly larvae feeding on oil-contained diet.With 2% inoculation of X8 broth,the survival rate of black soldier fly larvae increased from 90.17%,76.5%,and 48.33% to99.00%,88.5%,and 67.33% in 30%,40%,and 50% oil-containing chicken feeds,respectively.The survival rate of black soldier fly larvae increased from 96.33% to99.00%-99.67% in the real kitchen waste feeding experiment.The frass oil content reduced from 19.29% to 11.39%-7.39% and the grease removal rate increased from21.68% to 53.76%-69.98%.Inoculating X8 could significantly decrease the contents of oil in the frass,which could make residue in fine particles and easier to separate the larvae from the frass. |
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