Selection Of Bacillus Spp. Overproducing Xylanase And Studies On Enzymic Properties

Xylanase producing strains(Bacillus spp.) were isolated from ruminal contents in buffalo and goat.Isolates of Bacillus spp. were obtained and assayed for the xylanase activity with a method of transparent zones.L2-19 and Y25 strains presented the highest activity were selected for further investigation in detail.According to the morphological and physiological characteristics, two strains were identified as Bacills pumilus and Bacillus subtilis respectively.Based on the study of xylanase,the extracting methods and conditions of xylan from corn cob were improved. The virtue of the cooking method was integrated with the alkali extracting method. The main process of extracting consists of cooking, alkaline soak, and depositing. The content of hemicellulose in the crude xylan product is 63.4% and the ratio of extracting is 27.6%.The culture conditions that can influence the growth and enzyme production were investigated. The best condition for L2-19 produce xylanase were wheat bran used as carbon and yeast as nitrogen source. When wheat bran was used as carbon and (NH₄)₂SO₄ as nitrogen source,the xylanase production of Y25 reached the maximal.Both the strains reach maximum activity at intitial pH 6.0 and enough oxygen.The crude xylanase of L2-19 strain kept maximally active at pH7.0 and 50℃, be stable at pH6.0; and was stable over a wide pH range of 4.0-10.0.The crude enzyme of Y25 strain kept maximally active at pH6.0 and 50℃, be stable at pH6.0;and was stable over a wide pH range of 5.0-9.0. The crude enzyme of L2-19 and Y25 strains all kept stable below 40℃.