琼胶降解菌的筛选及其在龙须菜乙醇发酵中的初步应用

Isolations of agar-degrading bacteria and their function in ethanol fermentation from Gracilaria lemaneiformis

文章以龙须菜为原料,开展发酵产乙醇的基础研究,主要进行了高效琼胶降解菌的筛选和酶解条件的优化。利用琼胶为唯一碳源筛选出2株琼胶降解能力强的菌株QJ14和Hhjh,通过形态学观察和16s r DNA序列分析,对这两株菌株进行了鉴定,经NCBI数据库比对,确定QJ14为假单胞菌属,Hhjh为白色噬琼胶菌属。用QJ14和Hhjh产生的粗酶液酶解龙须菜酸解糊化液,并对影响酶解效果的因素,如起始p H值、酶解时间、震荡处理、混合酶液比例等进行了优化,结果还原糖产量最高可达29.33 mg/g。通过比较酵母单菌发酵、混合菌发酵与分步酶解发酵,利用顶空气相色谱法(HS-GC法)检测发酵液中乙醇产量,结果表明,酵母单菌发酵和混合菌发酵几乎没有乙醇产生,分步酶解发酵的乙醇产量约为2.36m L/L。

For the purpose of the optimal ethanol fermentation conditions of Gracilaria lemaneiformis,bacterial strains with strong agar-degrading abilities were isolated and their enzyme production conditions were studied. Using agar as the sole carbon source, two agar-degrading strains QJ14 and Hhjh were isolated. By compared with 16 S r DNA in NCBI database, QJ14 and Hhjh were identified as Pseudoalteromonas sp. QJ14 and Agarivorans sp. Hhjh, respectively. Hydrolyzed Gracilaria lemaneiformis with the crude agarase producing by QJ14 and Hhjh and then optimized hydrolysis conditions at different initial pH, enzymatic hydrolysis times, shaking conditions, mixed enzymes ratios. It could obtain maximum 29.33 mg/g reducing sugar. The hydrolysis product using enzymatic hydrolysis was significantly better compared with those of yeast fermentation and mixed culture fermentation. The ethanol production was analyzed as 2.36 mL/L using Head Space gas chromatography in enzymatic hydrolysis fermentation broth, while yeast fermentation broth and mixed culture fermentation broth were not measured. The experimental data provided laboratory references for the feasibility of the optimal Gracilaria lemaneiformis-ethanol fermentation conditions.