一组降解纤维素细菌的分离筛选及产酶特性研究

Screening a group of cellulose-degradation bacteria and their zymogenic characteristics

关键词:  纤维素降解  细菌  分离筛选  产酶特性  FPase  CMCase  混合发酵

Key words:  cellulose-degradation  bacteria  screening  zymogenic characteristics  FPase  CMCase  mixed fermation

摘要:

用稀释法从腐殖泥中分离菌株,根据它们在羧甲基纤维素钠(CMC-Na)-刚果红培养基上的透明圈直径及对滤纸的崩解能力,获得7株纤维素分解细菌(编号:B-37、B-35、B-31、B-25、B-17、Z-a和Z-b),其中菌株Z-b的纤维素崩解能力最强,分子鉴定结果表明它与Stenotrophomonas maltophilia的16S rDNA序列有99.8%的同源性,初步确定为嗜麦芽窄食单胞菌。适合7个菌株生长的C源为马铃薯浸出液,无机盐组分为:CaCl₂ 0.20、MgSO₄ 1.25、NaCl 5.00、(NH₄)₂SO₄ 1.30、KH₂PO₄ 1.35、FeSO₄·7H₂O 0.015、Na-EDTA 0.02 g/L。在滤纸为唯一碳源的培养基中,菌株Z-b的滤纸酶(FPase)和CMC酶(CMCase)活性最大,为0.099 U/mL和0.075 U/mL,而在固体PSA上,菌株B-31和B-37的FPase和CMCase活性最高,为0.131 U/mL和0.175 U/mL。7个细菌单独发酵,Z-b对滤纸的崩解能力最强,滤纸块完全崩解成粉未状; 与真菌34混合发酵,菌株组合Z-a+34、Z-b+34、B-31+34、B-25+34将滤纸完全水解为水溶性物质。可见,各菌株的纤维素酶活与培养条件密切相关,某些真菌、细菌间存在协同作用,它们混合发酵可大大提高纤维素的水解效率。

Abstract:

Bacterial strains were isolated from humus mud by employing the dilution methods. Seven cellulose-degradation strains marked as B-37,B-35,B-31,B-25,B-17,Z-a,and Z-b were selected according to the hyaloid rings on the medium of carboxymethylcellulose sodium(CMC-Na)- Congo red and their efficacy of decomposing filter paper. Z-b had the strongest ability in decomposing filter paper among the seven strains and 16S rDNA analyzed indecated that it was Stenotrophomonas maltophilia owning to 99.8% homology. Comparing clony size of the seven strains in media with different carbohydrates and inorganic salt,we found that the potato extract and inorganic salt which contained CaCl₂ 0.20,MgSO₄ 1.25,NaCl 5.00,(NH₄)₂SO₄ 1.30,KH₂PO₄ 1.35,FeSO₄·7H₂O 0.015,Na-EDTA 0.02(g/L)were suitable for the bacteria growth. Studying cellulase activity of 7 strains in different cultivation conditions,it's found that Z-b had the hightest filter paper(FPase)and CMC(CMCase)activity in the media which filter paper as the only carbohydrate. They were 0.099 and 0.075 U/mL. But on PSA medium,it was B-31and B-37 getting a highest cellulase activity. They were 0.131 and 0.175 U/mL. When fermented individually with filter paper,only Z-b could decompose the whole pieces of paper into powders. But when fermented with fungus 34,the combinations of Z-a+34,Z-b+34,B-31+34,and B-25+34 could hydrolyze the whole filter paper into water-soluble compounds. It was obvious that the cellulase activity of the seven strains closely related with their cultivation condition. Cooperation exists between some fungi and bacteria,it could greatly improve the efficiency of cellulose hydrolyzation when mixed fermentation.