| Microbial agents are currently widely used in industries such as agricultural production,sewage treatment,and food production.However,the short shelf life and low viable bacterial count of microbial agents are important factors that restrict their commercialization.Applying high-performance protective agents is an effective method to improve the shelf life and viable bacterial count of microbial agents.At present,the commonly used protective agents mainly include sugar substances such as trehalose and sucrose,protein substances such as skim milk powder,and alcohol substances such as glycerol.These substances have similarities in chemical structure with the substances that make up the cell membrane.Therefore,we speculate that these protective substances can effectively bind to the cell membrane,thereby preventing its oxidation and protecting microorganisms.The cell membrane is usually composed of proteins,sugars,and phospholipids.So do substances such as phospholipids,which are similar in composition to cell membranes,also have a protective effect on microorganisms?To address this issue,this article first investigated the possibility of substances such as cephalin and egg white powder as microbial protectants.This article first verifies the protective effects of phospholipids,sugar alcohols,and thickeners in liquid microbial inoculants.The results showed that proper amount of cephalin,egg white powder,maltose alcohol and trehalose were all good protectors for the preparation of liquid microbial agents.Among them,trehalose has the best effect,and the probiotic preparation can reach a live bacterial count of 2.26×10~8 cfu/m L after seven days.Moreover,the composite protective agent prepared by cephalin and trehalose has the best effect.After seven days of storage,the number of live bacteria can reach 4.7×10~8 cfu/m L,with a viable bacterial count of9.56×10~7cfu/m L after one month.At the same time,this composite protective agent can be used to prepare various microbial agents.The liquid microbial inoculants of Bacillus butyricum YN-5and Burkholderia gladioli XY-1 prepared with this protective agent had a viable bacterial count of 1.21×10~8 cfu/m L and 1.16×10~8 cfu/m L after one month.Through Fourier transform infrared spectroscopy analysis,we found that these protective agents have good protective effects because they can prevent functional bacteria from being oxidized under stress.This article prepared microbial solid bacterial agents using vacuum freeze-drying technology and first validated the possibility of phospholipids and egg white powder as protective agents for solid bacterial agents.The results indicate that these substances can all become protective agents for solid bacterial agents.Among them,the single protective agent with the best effect is egg white powder,and the prepared probiotic bacterial agent has a live bacterial count of 9.1×10~8 cfu/g after freeze-drying.The compound protective agent with the best effect is the protective agent compounded by trehalose,egg white powder,cephalin and maltose alcohol,and the initial number of viable bacteria is 3.65×10~9 cfu/g after freeze-drying,the number of viable bacteria can reach 1.32×10~9 cfu/g.The solid microbial inoculants of Bacillus butyricum YN-5 and Burkholderia gladioli XY-1 prepared with this protective agent achieved a viable count of 3.86×10~9cfu/g and 2.03×10~9cfu/g after one month.This article uses Fourier transform infrared spectroscopy and SEM to preliminarily study the protective mechanism of these protective agents on microorganisms.The results indicate that high-performance protective agents can form a complete coating film on the surface of microbial cells.When microorganisms are subjected to stress to produce reactive oxygen species,the protective agent will be oxidized first,thereby protecting the microorganisms from harm and achieving protective effects. |
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