Preparation Of Environment-friendly Soil Conservation Agent Poly Gamma-glutamic Acid Super Absorbent Resin

Poly-γ-glutamaic acid(γ-PGA) is a kind of biological macromolecules that made of L-and D-glutamic units linked through theα-amine and theγ-carboxylic acid groups,It is water-soluble,biodegradable,edible and non-toxic toward humans and the environment. Therefore,potential applications ofγ-PGA and its derivatives have been of interest in the past few years in the fields of medicine,food,cosmetic,plastics,and water treatment.Especially it can be the best substitute of undegradable hydrogel.In this article,the study began with theγ-PGA that B.licheniformisWBL-3 produced,used chemical and physical two methods to yield hydrogels,then studied the structure and its application in water retention properties of soil.This article deals with biosynthesis ofγ-PGA by fermentation with B.licheniformis WBL-3 which was reserved in our laboratory.The solid state fermentation was carried out for the production ofγ-PGA.The maximumγ-PGA production was 10.45g/kg.it was achieved in the conditions that describes as follows:the ratio of oybean dregs and wheat bran and nutrition liquid is 1:1:1(w/w),the best fermentate condition is:the incolnm the amount of substrate was 10%,the incolum was 20g,the initial pH was 7,the temperature was 37℃.A novel method was established to detectγ-PGA.A turbid solution was formed through the reaction betweenγ-PGA and cetylpyridinium chloride(CPC) and the turibidity was measured by using ultraviolet-visible spectroscopy at 680nm.The linearity between the concentration ofγ-PGA and its absorbance,the stability,repeatability and recovery of the method were studied. Through the reaction ofγ-PGA with CPC,a homogeneous turbid solution was formed.The turbid solution was stable in 3h under proper pH value and ion strength,the absorbance of the solution at 680nm had a good linear relationship with the concentration ofγ-PGA in the range 12.5-50ug/mL(R²=0.9939).The recovery was within the range of 86%-99.75%.Crosslinkedγ-PGA hydrogels were prepared by chemical method and by ⁶⁰Co-γ-irradiation.Compared the hydrogel made by chemical method and made by physical method,it is result that the hydrogel made by ⁶⁰Co-γ-irradiation has the higher water content.γ-PGA was crosslinked to yield high water sorption material with specific water content of about 1396 times their dry volume,it was achieved in the conditions that describes as follows: irradiation dose was 25KGy,γ-PGA concentration was 8%,pH9.0.The application ofγ-PGA in agricultural filed was studied,γ-PGA could absorb 900 times water in solid,theγ-PGA solution had better water-holding and sustained release ability.