Screening Of Lactic Acid Bacteria That CAN Convert Xylan To Lactic Acid And Study On The Lactic Acid Fermentaion Of Corn Stalk

Based on the abundant renewable biomass resources in China, especially the residues from agriculture, such as stems, stalks and leaves etc, corn stalks are selected as raw material for lactic acid production. Through a systematic study on the lactic acid fermentation of CBP,the following results and achievements are obtained.1)Lactic acid bacteria L3 and L6, with a high ability to convert xylan to lactic acid, were isolated from the nature. The yields of lactic acid were 2.25g/l and 1.67g/l, respectively.2) After the Physiological and biochemical characteristic identification, especially using the Intelligent Bacteria Identification System, L3 was identified as Lactobacillus pentosus (confidence level 96.2%) and L6 was identified as Streptococcus avium(confidence level 97.6%).3) L. pentosus L3,S. avium L6 were induced by ultraviolet and DES, the mutation strains L. pentosus L35-6å’ŒS. avium L64-6 were screened out, by which lactic acid production could respectively increase 58.2% and 44.0%, were 71.2g/l and 48.1 g/l.4) the optimal reaction condition for Lactic acid production was: peptone 6g/l, yeast extract paste 3g/l, beef extract 4g/l,K₂HPO₄3g/l,MgSO₄0.3g/l,FeSO₄0.2g/l. The optimum fermentation condition was: temperature 40℃,pH6.5,media value 75ml/250ml,60r/min shaking ferment for 72 hours.5) On the lactic acid solid state fermentation, the single strain L. pentosus L35-6 was better than S. avium L64-6 on depredating hemicellulose, and the strain S. avium L64-6 was better on depredating cellulose. In the initial 8 hours, the value of depredating hemicellulose was stronger. The two strains ferment together; lactic acid yield can be 18.2g/l,were increase 42.2%å’Œ55.6%, respectively. And the value of depredation were increase too, were 56.42% and 78.56%.