Screening,Identification And Growth Condition Optimization Of An Alkalophilic Strain For Lignin Degradation

Lignin is abundant in nature and it is the main ingredient of the plant. The degradation, conversion and use of lignin play important roles in the waste water treatment and resource recycling. Lignin is mainly composed of carbon, hydrogen, oxygen elements, forming complex mesh aromatic polymer compound. And the lignin does not dissolve in water or neutral organic. It is soluble under alkaline condition. The ideal situation is that the lignin could be degraded under alkaline conditions. At the same time, the bacteria favor alkaline condition, grow rapidly and there are wide sources of them. Then the chemical properties and biological characteristics would be combined when lignin is degraded by bacteria.This issue aims to screen and identify alkalophilic bacterium for lignin degradation. Then the growth condition of strain is optimized and the thin-layer chromatography is used for lignin degradation effect.1.The strains were isolated from three different environmental samples, the waste water of Yingkou paper mill, the trees rotting from campus and the waste water of Dalian Jinlida Food Co., Ltd.(konjac manufacturer), respectively. Screening an alkalophilic strain can grow in the medium of lignin as sole carbon source. The strain was marked as ⅢS3.2. The alkalophilic strain is Gram-positive bacteria, named Bacillus cohnii ⅢS3, based on Gram’s stain and the phylogenetic theory of16S rDNA sequence. The sequence identity of the strain and Bacillus is99%.3. Through single factor, orthogonal and compounded carbons cometabolism tests, the growth conditions of Bacillus cohnii IIIS3was optimized.Single factor test changes the culture conditions of the alkalophilic strain, such as lignin concentration of medium, pH, temperature and rotational speed, to explore the strains of Bacillus cohnii IIIS3optimum growth conditions.The result was0.10%lignin concentration, pH=10.0,37℃and140r/min.The impact of each factor on the Bacillus cohnii IIIS3growth was explored by orthogonal test. The optimal combination of conditions are0.10%lignin concentration, pH=10.0,37℃and120r/min. The most important factor of alkalophilic strain growth is the pH.When the lignin concentration was0.1%(w/v) in the composite carbon source medium and the concentration of glucose was different, the Bacillus cohnii IIIS3strain grew fast during0-10h. Because of the use of glucose metabolism in a lactic acid, the pH of the medium reduced and the growth of the alkalophilic strains was affected. Fermenter culture instead of shake flasks, the pH was constant artificially.Then the advantage of complex carbon sources fermentation came out, the strain was in the better state of growth. As a consequence, Bacillus cohnii IIIS3has a certain effect on the degradation of lignin according to TLC.The issue screened an alkalophilic strain named Bacillus cohnii IIIS3and optimized growth conditions of it. Batch culture with the fermenter, the fermentation liquid was analyzed by thin layer chromatography confirmed that the strain made lignin degrade.