Study On The Enhanced Protein Synthesis Of Hermetia Illucens From Kitchen Waste Via Biological Pretreatment

Kitchen waste is the main component of urban organic solid waste in China,which has the characteristics of large quantity,high organic matter content and good bioavailability.With the gradual improvement of collection and transportation system for kitchen waste,the recycling treatment with high added-value represents current development tendency.The conversion of organic waste into protein resources,mediated by exploitable insects such as Hermetia illucens has attracted much attention in recent years.Since kitchen waste mainly contained macromolecular organic matter including starch,protein and cellulose,how to enhance the absorption and conversion capacity of Hermetia illucens deserves further research.Given the consideration above,this paper proposed the pretreatment on kitchen waste via enzymes and probiotics,to promote the metabolism of Hermetia illucens and improve its yield and quality of protein.By the comparative studies on organic matter degradation,larva growth and intestinal flora evolution,the effects of the two biological pretreatment technologies on the treatment efficiency and protein synthesis of Hermetia illucens were elucidated.The studies could provide profitable ideas for kitchen waste treatment with the principle of“reduction”,“innocuity”and“recycling”.The main findings are as follows:（1）The pretreatment via protease and amylase increased the bioavailability of kitchen waste and improved the metabolic activity of intestinal flora in Hermetia illucens,and further enhanced the larva growth and its protein synthesis.By contrast,the amylase pretreatment group had the optimum effect.In the control group,the average single larva weight,larva yield and protein yield were 111.78 mg,0.16 g/g-TS_consumed and 0.08 g/g-TS_consumed,respectively.The degradation efficiencies of dry matter,starch and crude protein were respectively 54.0%,62.8%and 53.0%.In the amylase pretreatment group,the average single larva weight,larva yield and protein yield reached 208.42 mg,0.25 g/g-TS_consumed and 0.14 g/g-TS_consumed,which was increased by 0.86,0.56 and 0.75 times,respectively.The degradation efficiencies of dry matter,starch and crude protein reduction of kitchen waste reached 71.70%,77.86%and 65.90%,respectively with their increase of 0.32,0.24 and 0.24 times.The amylase pretreatment changed the structure of intestinal flora in Hermetia illucens transforming kitchen waste.Enterococcus and Sporosarcina became the dominant genera,and the metabolic function of intestinal flora was significantly enhanced.The highest intestinal amylase and protease activities reached 948and 355 U/m L,respectively with the increase of 33.5%and 26.8%compared with the control group.（2）The pre-fermentation of probiotic bacteria could also effectively enhance protein synthesis of Hermetia illucens.The combination of Lactobacillus,Bacillus subtilis and Saccharomyces cerevisiae significantly improved the soluble protein content of kitchen waste.By 40 h pre-fermentation,the soluble protein content reached 224.02 mg/g,which was 5.06times higher than raw material.Compared with the amylase pre-treatment group,the synergistic pre-fermentation group of the three probiotics had a slightly better effect on Hermetia illucens metabolism.The average single larva weight,larva yield and protein yield reached reached221.15 mg,0.28 g/g-TS_consumed and 0.16 g/g-TS_consumed,respectively.The degradation efficiencies of dry matter,starch and crude protein respectively reached 74.10%,78.92%and68.33%.At the fast proliferation phase,the relative abundance of Sporosarcina and Corynebacterium in the intestinal flora increased to 32.74%and 15.36%,respectively.The highest intestinal amylase and protease activities reached 983 and 401 U/m L.（3）The two biological pretreatment methods of kitchen waste both improved the in vitro antioxidant activity of Hermetia illucens proteins.The protein of Hermetia illucens was extracted by alkali solubilization and acid precipitation method,and the extraction efficiency could reach 79.90%-84.76%.The total reducing powers of larva protein,obtained from amylase pretreatment group and probiotic pre-fermentation group,were 1.07 and 1.14 times higher than that in the control group,respectively.The scavenging capacities on superoxide anion radical were both between Vc and OVA,which were significantly higher than that in the control group.In the amylase pretreatment group,the IC₅₀ values of the larva protein obtained,representing the scavenging activities on DPPH,hydroxyl,ABTS radical and ferrous ion chelating ability,were respectively 3.87 mg/m L,2.65 mg/m L,0.28 mg/m L and 0.97 mg/m L,which were 1.18,1.16,1.11 and 1.11 times higher than those of the control.Moreover,those IC₅₀ values of the larva protein obtained from probiotic pre-fermentation group were respectively 3.03 mg/m L,2.65 mg/m L,0.25 mg/m L and 0.89 mg/m L,which were 1.51,1.16,1.24 and 1.21 times higher than those of the control.