降柠檬酸菌株的筛选及鉴定

Study on isolation and identification of reducing citric acid strains

为筛选具有降柠檬酸能力的酵母菌株,对一柠檬酸厂废水废渣中的微生物进行培养分离纯化保藏,共获得具有耐柠檬酸的菌株15株。对15株菌株的降柠檬酸能力进行测试,发现5株菌的降柠檬酸能力较强,发酵5d可降解柠檬酸培养基中70%以上的柠檬酸。测定5株菌的酒精耐受性,菌株NS2、NL2的酒精耐受能力较强。观察该两株菌的形态学及生理生化特性,将NS2鉴定为毕赤酵母菌,NL2鉴定为热带假丝酵母菌。进一步通过分子生物手段进行18SrDNA PCR测序分析,将NS2鉴定为Pichia kudriavzevii,NL2鉴定为Candida tropicalis。研究成果可为今后应用生物降酸法降低山楂酒等果酒中有机酸含量提供指导。

In order to screen the strains which have the capability of reducing the citric acid, 15 strains of yeasts were isolated from the materials of waste water and waste residue. The waste water and res- idue were collected in the citric acid factory. The yeasts were screened based on the capability of fermenting the citric acid. It was found that the 5 strains had good capability of reducing the citric acid. They could reduce at least 70% citric acid of the culture medium after 5 d fermentation. The 5 strains were tested the stress resistance of ethanol. The strain NS2 and NL2 have strong stress resistance.The morphological and physiology characteristics of NS2 and NL2 were measured by microscopic observation, assimilation of carbon and nitrogen. Then the two strains were identified by 18S rDNA se- quencing and the phylogenetic analysis. In the end, NS2 was identified as Pichia kudriavzevii, NL2 was identified as Candida tropicalis. They can be used in the technology of acid reduction in the hawthorn wine in the future.