| Straw is a byproduct of agricultural production,but also an important biomass resource.In recent years,the state has called for"establishing a big food concept",asking for protein from plants,animals and microorganisms,and developing food resources in various ways.Yellow mealworm is a kind of high-protein insect with high economic value that is easy to feed and has the ability to degrade straw.Penicillium phosphorolyticum(PA01)has the dual function of lignocellulose degradation and phosphorus solubilization,and can be used in agricultural production as a phosphorus solubilizing agent.In order to utilize straw in a green and high-value way,this study used yellow mealworms to treat straw coupled with insect feces to cultivate Penicillium solani,and explored the efficiency and mechanism of coupling yellow mealworms and Penicillium solani to transform different kinds of straw from the perspectives of straw structural characteristics,chemical composition,gut microbial community of yellow mealworms,metabolites and metabolic pathways of Penicillium solani,and co-production of insect body protein and phosphate solubilizing bacterial agent.The main findings are as follows:(1)The utilization rate,frass yield and mealworm’s fresh weight gain rate of four different straw species treated with yellow mealworms,including WHS,CS,RS and SS,showed that WHS>CS>RS>SS.There were significant differences in the degree of lignocellulose degradation of the four different types of straw by yellow mealworms.The analysis of straw structural properties showed that the hardness and chewiness of WHS,CS,RS and SS increased in order.The yellow mealworm treatment efficiency was highly significantly negatively correlated with straw hardness,chewiness and crystallinity(Cr I),and significantly negatively correlated with cellulose and lignin content and positively correlated with protein content.Supplementation with exogenous protein increased straw utilization by 8.00%,11.3%and 50.6%,and increased worm manure yield by 22.8%,17.9%and 63.6%,for CS,RS and SS,and increased the percentage of essential amino acids in worm protein by 0.0958%～6.59%.It showed that both the structural properties and chemical components of straw significantly affected the transformation behavior and efficiency of yellow mealworms.(2)The dominant lignocellulose-degrading genera such as Erwinia,Enterococcus and Clostridium were present in the gut flora of yellow mealworms reared on different species of straw.Proteobacteria(35.3%～65.8%)and Firmicurium(24.9%～62.4%)were the main phyla of the gut microorganisms of yellow mealworms with straw as the only substrate,and different types of straw influenced the relative abundance of Erwinia,Enterococcus and Lactococcus in the intestinal flora of yellow mealworms.Spearman’s correlation analysis showed that there was a significant correlation between the dominant genus of yellow meal worm intestinal bacteria and straw utilization,frass yield,larva dry weight,cellulose digestibility,hemicellulose digestibility and lignin digestibility.(3)The viable counts of the phosphorus solubilizing Penicillium in different straw manure cultures were in the following order:CS>SS>RS>WHS,and the highest viable count was 7.90×10~6CFU/m L with CS frass as the substrate.The dry weight of phosphorus solubilizing bacteria obtained by transforming unit mass of frass at the end of the culture was:SS(0.220 g/g)>RS(0.215 g/g)>CS(0.207 g/g)>WHS(0.190 g/g).The organic acids secreted during the culture of Penicillium phosphorolyticum were mainly acetic acid,oxalic acid,citric acid,malic acid,succinic acid and gluconic acid.Whole gene sequencing revealed the presence of genes encoding lignocellulose-degrading enzymes such as endo-β-1,4-glucanase,cellulose hydrolase,glutamate peptide-S-transferase,and key enzymes for organic acid secretion such as citrate synthase and malate dehydrogenase in Penicillium phosphorolyticum PA01,elucidating the mechanism underlying the dual functions of lignocellulose degradation and acid phospholysis in Penicillium phosphorolyticum.(4)The phosphorus solubilization amount of phosphorus solubilizing Penicillium phosphosolubilis cultured in different kinds of straw and frass was CS(894 mg/L)>RS(680 mg/L)>WHS(639 mg/L)>SS(630 mg/L),and the corresponding phosphorus solubilization amount of strain cultured in conventional potato dextrose medium(PDB)was 582 mg/L,indicating that phosphorus solubilizing Penicillium phosphorolyticum cultured in straw and frass had good phosphorus solubilizing ability.Penicillium has good phosphorus solubilization ability,and the frass can replace potato glucose medium to prepare phosphorus solubilizing penicillium.(5)The material balance of the coupled transformation of different types of straw by yellow mealworm and Penicillium phosphosolubilis showed that the yield of frass per unit mass of straw transformed by yellow mealworm was:RS(0.841 g/g)>WHS(0.834g/g)>CS(0.815 g/g)>SS(0.702 g/g);correspondingly,the yield of straw per unit mass transformed by Penicillium phosphosolubilis was solid fungicides were:RS(0.149 g/g)>CS(0.143 g/g)>WHS(0.140 g/g)>SS(0.112 g/g).In a comprehensive evaluation,the coupled transformation of CS and RS by yellow mealworm and Penicillium phosphosolubilis was more effective than that of WHS and SS. |
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