枯草芽孢杆菌发酵甘草渣产2,3-丁二醇和乙偶姻的初步研究

Fermentation of 2,3-butanediol and acetoin from liquorice residue using Bacillus subtilis

摘要:

甘草渣是甘草提取完活性成分后的剩余物，富含木质纤维素。以甘草渣为研究对象，以2种稀碱（Na2CO3水溶液和NaOH水溶液）以及稀碱（Na2CO3水溶液或NaOH水溶液）和醋酸乙醇胺离子液体混合液为溶剂对甘草渣进行预处理，研究不同碱浓度和预处理温度对甘草渣组成及酶解效果的影响。结果表明，质量分数2%的NaOH水溶液在固液比（w/v）1:10（即每克甘草渣加入10毫升溶剂）、100 ℃条件下预处理甘草渣1.5 h，木质素去除率达54.1%、纤维素回收率为77.2%；样品酶解24 h，葡萄糖得率可达53.5%，较预处理前甘草渣（10.6%）提高了4.0倍。最后，对预处理后的甘草渣进行高固酶解，在固液比3:10、酶用量45 FPU/g生物质条件下酶解72 h，葡萄糖产量达到86.2 g/L、木糖18.9 g/L。以此酶解液为碳源进行发酵，96 h后发酵液中2,3-丁二醇和乙偶姻总产量为43.9 g/L，还原糖转化率为0.42 g/g；与对照组相比，酶解液更有利于菌体生长，生产强度提高，但转化率略低。

Abstract:

Liquorice residue, the residue of liquorice after the extraction of active ingredients, is rich in lignocellulose. The liquorice residue was pretreated with two dilute basic solutions (Na2CO3 aqueous solution and NaOH aqueous solution) and the mixtures of dilute basic solution (Na2CO3 aqueous solution or NaOH aqueous solution) and ethanolamine acetate, and the effects of different base concentrations and pretreatment temperatures on the composition and enzymatic hydrolysis of liquorice residue were studied. The results showed that the lignin removal reached 54.1% and cellulose recovery rate was 77.2% when the liquorice residue was pretreated with 2% (mass fraction) NaOH aqueous solution with a solid-liquid ratio (w/v) of 1:10 (i.e., 10 ml of solvent per gram of liquorice residue) for 1.5 h at 100 ℃, and the glucose yield was 53.5% after 24-h enzymatic digestion which was 4.0 times higher than that without pretreatment (10.6%). When the pretreated liquorice residue was subjected to high solid enzymatic digestion at a solid-liquid ratio of 3:10 with an enzyme dosage of 45 FPU/g of biomass for 72 h, the glucose concentration reached 86.2 g/L and xylose was 18.9 g/L. Using this hydrolysate as the carbon source for fermentation, the total production of 2,3-butanediol and acetoin was 43.9 g/L after 96-h fermentation, and the conversion rate was 0.42 g/g. Compared with the control group, the hydrolysate was more favorable to the growth of the bacteria, and the productivity of 2,3-butanediol and acetoin was increased, while the conversion rate was slightly lower.