Abstract

Optimization of pretreatment and saccharification of Sorghum durra stalk (Sds) was carried out. The chimeric enzyme (CtGH1-L1-CtGH5-F194A) having β-glucosidase (CtGH1) and endo β-1,4 glucanase activity (CtGH5-F194A) and cellobiohydrolase (CtCBH5A) from Clostridium thermocellum were used for saccharification. Chimeric enzyme will save production cost of two enzymes, individually. Stage 2 pretreatment by 1% (w/v) NaOH assisted autoclaving + 1.5% (v/v) dilute H₂SO₄ assisted oven heating gave lower total sugar yield (366.6 mg/g of pretreated Sds) and total glucose yield (195 mg/g of pretreated Sds) in pretreated hydrolysate with highest crystallinity index 55.6% than the other stage 2 pretreatments. Optimized parameters for saccharification of above stage 2 pretreated biomass were 3% (w/v) biomass concentration, enzyme (chimera: cellobiohydrolase) ratio, 2:3 (U/g) of biomass, total enzyme loading (350 U/g of pretreated biomass), 24 h and 30 °C. Best stage 2 pretreated Sds under optimized enzyme saccharification conditions gave maximum total reducing sugar yield 417 mg/g and glucose yield 285 mg/g pretreated biomass in hydrolysate. Best stage 2 pretreated Sds showed significantly higher cellulose, 71.3% and lower lignin, 2.0% and hemicellulose, 12.2% (w/w) content suggesting the effectiveness of method. This hydrolysate upon SHF using Saccharomyces cerevisiae under unoptimized conditions produced ethanol yield, 0.12 g/g of glucose.

Abbreviation: Ct-Clostridium thermocellum, Sds-Sorghum durra stalk, TRS-Total reducing sugar, HPLC-High performance liquid chromatography, RI-Refractive index, ADL-acid insoluble lignin, GYE-Glucose yeast extract, MGYP-Malt glucose yeast extract peptone, SHF-separate hydrolysis and fermentation, OD-Optical density, PVDF-Poly vinylidene fluoride, TS-total sugar, FESEM-Field emission scanning electron microscopy, XRD-X-ray diffraction, FTIR-Fourier transform infra-red spectroscopy and CrI-Crystallinity index.

摘要

对高粱茎秆（Sds）的预处理和糖化进行了优化。具有β-葡糖苷酶（Ct GH1）和内切β-1,4葡聚糖酶活性（Ct GH5-F194A）的嵌合酶（Ct GH1-L1- Ct GH5- F194A）和热纤梭菌的纤维二糖水解酶（Ct CBH5A）用于糖化。 。嵌合酶将分别节省两种酶的生产成本。1％（w / v）NaOH辅助高压灭菌+ 1.5％（v / v）稀H ₂ SO ₄预处理的第2阶段在其他最高的结晶度指标为55.6％的预处理水解产物中，辅助烤箱加热在较低的结晶度下提供了更低的总糖产量（366.6 mg / g预处理Sds）和总葡萄糖产率（195 mg / g预处理Sds）。糖化上述第2阶段预处理生物质的最佳参数为3％（w / v）生物质浓度，酶（嵌合体：纤维二糖水解酶）比，2：3（U / g）生物质，总酶载量（350 U / g预处理）生物质），24小时和30°C。在优化的酶糖化条件下，最佳的阶段2预处理Sds在水解产物中的最大还原糖总产量为417 mg / g，葡萄糖总产量为285 mg / g。最佳阶段2预处理的Sds显示纤维素含量高得多，为71.3％，木质素含量为2.0％，半纤维素含量为12.2％（w / w），表明该方法有效。在未优化的条件下，酿酒酵母产生乙醇产量，葡萄糖为0.12 g / g。

缩写： Ct-Clostridium thermocellum，Sds - Sorghum durra stalk，TRS-总还原糖，HPLC-高效液相色谱，RI-折射率，ADL-酸不溶性木质素，GYE-葡萄糖酵母提取物，MGYP-麦芽葡萄糖酵母提取物蛋白ept ，SHF-单独的水解和发酵，OD-光密度，PVDF-聚偏二氟乙烯，TS-总糖，FESEM场发射扫描电子显微镜，X射线衍射X射线衍射，FTIR-傅立叶变换红外光谱法和值CrI -结晶度指数。