Screening And Identification Of Chitinase-producing Bacteria From Cicada Flower Soil And Its Enzyme-producing Capability Analysis

Chitin is widely distributed in nature and is a nitrogen-containing polysaccharide whose content is second only to cellulose in nature.The insoluble nature of chitin in water limits its application to a certain extent.Chitin resources such as shrimp shells and crab shells are often treated as waste due to their complex extraction process.The use of chitinase,a green and pollution-free biological enzymatic method,can catalyze ?-1,4 glycosidic bonds in chitin molecules to degrade chitin to produce chitin oligosaccharides,N-acetyl-D-glucosamine and other substances.Known to all,the degradation products of chitin,chitosan oligosaccharides,N-acetyl-D-glucosamine and their derivatives are widely used in the fields of medicine,food and agriculture and have high value.During the formation of cicada flowers,parasitic fungi rely on the help of chitinase to invade cicada larvae,and chitin is the main component in the outer shell of cicada larvae.Therefore,this study selected a few chitinase producing bacteria from the rhizosphere soil of cicada flowers.The chitinase producing strain W1 was identified by 16 S r DNA sequencing.The enzyme-producing type,enzymatic properties and enzyme-producing conditions of the strain were also explored here.1.Using colloidal chitin as the sole carbon source,two bacterial strains with strong chitinase-producing ability were selected from the cicada flower soil collected in the mountainous area of Anji County,Huzhou City,Zhejiang Province,and named as W1 and W2;The morphological and molecular biological identification of the bacterial strains confirmed that the two strains were Serratia marcescens.The W1 strain produces a red pigment when it is cultured at 30°C.2.The chitinase produced by the W1 strain was identified by Native-PAGE and mass spectrometry,and the mass spectrometry results were searched and compared with the Serratia marcescens protein database,and 10 chitinases were successfully identified.The number of peptides was 10-18,the length of the encoded amino acid was 479?563,and the molecular weight was between 51.6 and 61.1k Da.At the same time,the study determined the enzymatic characteristics of the chitinase produced by W1.The optimum temperature of chitinase was 45?,maintain high stability at 35?;the optimum p H value of the chitinase was 5.0,maintain relatively high stability in the p H 5.0?11.0.3.Using single factor and response surface tests to optimize the enzyme production conditions of the W1 strain,it was finally determined that the best enzyme production conditions were that the initial p H of the medium was 5.1,the culture temperature was29.7°C,and the culture time was 3.8 days.Under these conditions,the strain The enzyme activity of chitinase produced by W1 is 0.523 U/m L,and the optimized enzyme activity is1.71 times higher than before.