Biomass Conversion Research Laboratory, Department of Chemical Engineering and Materials Science, Michigan State University, 3900 Collins Road, Lansing, MI 48910-8596, USA.
Biotechnol Biofuels. 2009 Nov 24;2(1):29. doi: 10.1186/1754-6834-2-29.
Corn stover composition changes considerably throughout the growing season and also varies between the various fractions of the plant. These differences can impact optimal pretreatment conditions, enzymatic digestibility and maximum achievable sugar yields in the process of converting lignocellulosics to ethanol. The goal of this project was to determine which combination of corn stover fractions provides the most benefit to the biorefinery in terms of sugar yields and to determine the preferential order in which fractions should be harvested. Ammonia fiber expansion (AFEX) pretreatment, followed by enzymatic hydrolysis, was performed on early and late harvest corn stover fractions (stem, leaf, husk and cob). Sugar yields were used to optimize scenarios for the selective harvest of corn stover assuming 70% or 30% collection of the total available stover.
The optimal AFEX conditions for all stover fractions, regardless of harvest period, were: 1.5 (g NH3 g-1 biomass); 60% moisture content (dry-weight basis; dwb), 90 degrees C and 5 min residence time. Enzymatic hydrolysis was conducted using cellulase, beta-glucosidase, and xylanase at 31.3, 41.3, and 3.1 mg g-1 glucan, respectively. The optimal harvest order for selectively harvested corn stover (SHCS) was husk > leaf > stem > cob. This harvest scenario, combined with optimal AFEX pretreatment conditions, gave a theoretical ethanol yield of 2051 L ha-1 and 912 L ha-1 for 70% and 30% corn stover collection, respectively.
Changing the proportion of stover fractions collected had a smaller impact on theoretical ethanol yields (29 - 141 L ha-1) compared to the effect of altering pretreatment and enzymatic hydrolysis conditions (150 - 462 L ha-1) or harvesting less stover (852 - 1139 L ha-1). Resources may be more effectively spent on improving sustainable harvesting, thereby increasing potential ethanol yields per hectare harvested, and optimizing biomass processing rather than focusing on the selective harvest of specific corn stover fractions.
玉米秸秆的组成在整个生长季节都会发生很大变化，而且在植物的不同部位之间也存在差异。这些差异会影响预处理条件的优化、酶解的可消化性以及将木质纤维素转化为乙醇的最大产糖量。本项目的目的是确定哪种玉米秸秆组分的组合最有利于生物炼制厂在产糖量方面的效益，并确定应优先收获的组分顺序。采用氨纤维膨胀（AFEX）预处理，然后进行酶水解，对早期和晚期收获的玉米秸秆组分（茎、叶、壳和芯）进行处理。根据假设收集总可用秸秆的 70%或 30%，使用糖产量来优化选择性收获玉米秸秆的方案。
所有秸秆组分（无论收获期如何）的最佳 AFEX 条件均为：1.5（g NH3 g-1 biomass）；60%（干重基础；dwb）水分含量，90°C 和 5 分钟停留时间。纤维素酶、β-葡萄糖苷酶和木聚糖酶的酶解条件分别为 31.3、41.3 和 3.1 mg g-1 葡聚糖。选择性收获玉米秸秆（SHCS）的最佳收获顺序为壳>叶>茎>芯。这种收获方案与最佳 AFEX 预处理条件相结合，对于 70%和 30%的玉米秸秆收集，理论乙醇产量分别为 2051 L ha-1 和 912 L ha-1。
与改变预处理和酶解条件（150-462 L ha-1）或减少秸秆收获量（852-1139 L ha-1）相比，改变收集的秸秆组分比例对理论乙醇产量的影响较小（29-141 L ha-1）。资源可能更有效地用于提高可持续收获，从而提高每公顷收获的潜在乙醇产量，并优化生物质加工，而不是专注于特定玉米秸秆组分的选择性收获。
