Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, DTU, Denmark.
Biotechnol Biofuels. 2013 Aug 14;6:116. doi: 10.1186/1754-6834-6-116. eCollection 2013.
Ensiling is a well-known method for preserving green biomasses through anaerobic production of organic acids by lactic acid bacteria. In this study, wheat straw is subjected to ensiling in combination with hydrothermal treatment as a combined pretreatment method, taking advantage of the produced organic acids.
Ensiling for 4 weeks was accomplished in a vacuum bag system after addition of an inoculum of Lactobacillus buchneri and 7% w/w xylose to wheat straw biomass at 35% final dry matter. Both glucan and xylan were preserved, and the DM loss after ensiling was less than 0.5%. When comparing hydrothermally treated wheat straw (170, 180 and 190°C) with hydrothermally treated ensiled wheat straw (same temperatures), several positive effects of ensiling were revealed. Glucan was up-concentrated in the solid fraction and the solubilisation of hemicellulose was significantly increased. Subsequent enzymatic hydrolysis of the solid fractions showed that ensiling significantly improved the effect of pretreatment, especially at the lower temperatures of 170 and 180°C. The overall glucose yields after pretreatments of ensiled wheat straw were higher than for non-ensiled wheat straw hydrothermally treated at 190°C, namely 74-81% of the theoretical maximum glucose in the raw material, which was ~1.8 times better than the corresponding yields for the non-ensiled straw pretreated at 170 or 180°C. The highest overall conversion of combined glucose and xylose was achieved for ensiled wheat straw hydrothermally treated at 180°C, with overall glucose yield of 78% and overall conversion yield of xylose of 87%.
Ensiling of wheat straw is shown to be an effective pre-step to hydrothermal treatment, and can give rise to a welcomed decrease of process temperature in hydrothermal treatments, thereby potentially having a positive effect on large scale pretreatment costs.
青贮是一种通过乳酸菌产生有机酸来实现绿色生物质厌氧生产的知名方法。在这项研究中，小麦秸秆经过水热处理与青贮相结合的预处理方法，利用所产生的有机酸。
在最终干物质含量为 35%的条件下，向小麦秸秆生物质中添加戊糖糖和 7%w/w 的植物乳杆菌发酵剂，然后在真空袋系统中进行 4 周青贮。结果发现，纤维素和木聚糖都得到了保留，青贮后的干物质损失小于 0.5%。与水热处理的小麦秸秆（170、180 和 190°C）相比，水热处理的青贮小麦秸秆（相同温度）具有几个青贮的积极效果。纤维素在固体部分中被浓缩，半纤维素的溶解率显著提高。随后对固体部分进行酶解，结果表明青贮显著提高了预处理的效果，尤其是在 170 和 180°C 的较低温度下。经青贮预处理的小麦秸秆的总葡萄糖产率高于未经青贮、在 190°C 下进行水热处理的小麦秸秆，即达到原料中理论最大葡萄糖的 74-81%，比未经青贮、在 170 或 180°C 下进行水热处理的对应产率高出约 1.8 倍。在 180°C 下进行水热处理的青贮小麦秸秆的总葡萄糖和木糖的综合转化率最高，总葡萄糖产率为 78%，木糖总转化率为 87%。
青贮小麦秸秆是水热处理的有效预处理步骤，可以降低水热处理的温度，从而可能对大规模预处理成本产生积极影响。
