Maurya Devendra Prasad, Singla Ankit, Negi Sangeeta
Department of Biochemistry and Biochemical Engineering, Sam Higginbottom Institute of Agriculture, Technology and Sciences, Allahabad, 211-007, Uttar Pradesh, India.
Department of Microbiology and Fermentation Technology, Sam Higginbottom Institute of Agriculture, Technology and Sciences, Allahabad, 211-007, Uttar Pradesh, India.
3 Biotech. 2015 Oct;5(5):597-609. doi: 10.1007/s13205-015-0279-4. Epub 2015 Feb 3.
Second-generation bioethanol can be produced from various lignocellulosic biomasses such as wood, agricultural or forest residues. Lignocellulosic biomass is inexpensive, renewable and abundant source for bioethanol production. The conversion of lignocellulosic biomass to bioethanol could be a promising technology though the process has several challenges and limitations such as biomass transport and handling, and efficient pretreatment methods for total delignification of lignocellulosics. Proper pretreatment methods can increase concentrations of fermentable sugars after enzymatic saccharification, thereby improving the efficiency of the whole process. Conversion of glucose as well as xylose to bioethanol needs some new fermentation technologies to make the whole process inexpensive. The main goal of pretreatment is to increase the digestibility of maximum available sugars. Each pretreatment process has a specific effect on the cellulose, hemicellulose and lignin fraction; thus, different pretreatment methods and conditions should be chosen according to the process configuration selected for the subsequent hydrolysis and fermentation steps. The cost of ethanol production from lignocellulosic biomass in current technologies is relatively high. Additionally, low yield still remains as one of the main challenges. This paper reviews the various technologies for maximum conversion of cellulose and hemicelluloses fraction to ethanol, and it point outs several key properties that should be targeted for low cost and maximum yield.
第二代生物乙醇可以由各种木质纤维素生物质生产，如木材、农业或森林残留物。木质纤维素生物质是生产生物乙醇的廉价、可再生且丰富的来源。尽管将木质纤维素生物质转化为生物乙醇的过程存在若干挑战和限制，如生物质的运输和处理，以及对木质纤维素进行完全脱木质素的高效预处理方法，但这仍可能是一项有前景的技术。适当的预处理方法可以在酶解糖化后提高可发酵糖的浓度，从而提高整个过程的效率。将葡萄糖以及木糖转化为生物乙醇需要一些新的发酵技术，以使整个过程成本低廉。预处理的主要目标是提高最大可利用糖的消化率。每个预处理过程对纤维素、半纤维素和木质素部分都有特定的影响；因此，应根据为后续水解和发酵步骤选择的工艺配置来选择不同的预处理方法和条件。在当前技术中，从木质纤维素生物质生产乙醇的成本相对较高。此外，低产量仍然是主要挑战之一。本文综述了将纤维素和半纤维素部分最大限度转化为乙醇的各种技术，并指出了为实现低成本和高产量应针对的几个关键特性。
