PDF(Sci-hub)
Abstract：
BACKGROUND: Liquid hot water (LHW) pretreatment has been considered as one of the most industrially viable and environment-friendly methods for facilitating the transformation of lignocelluloses into biofuels through biological conversion. However, lignin fragments in pretreatment hydrolysates are preferential to condense with each other and then deposit back onto cellulose surface under severe conditions. Particularly, lignin tends to relocate or redistribute under high-temperature LHW pretreatment conditions. The lignin residues on the cellulose surface would result in significant nonproductive binding of cellulolytic enzymes, and therefore negatively affect the enzymatic conversion (EC) of glucan in pretreated substrates. Although additives such as bovine serum albumin (BSA) and Tween series have been used to reduce nonproductive binding of enzymes through blocking the lignin, the high cost or non-biocompatibility of these additives limits their potential in industrial applications.
RESULTS: Here, we firstly report that a soluble soy protein (SP) extracted from inexpensive defatted soy powder (DSP) showed excellent performance in promoting the EC of glucan in LHW-pretreated lignocellulosic substrates. The addition of the SP (80 mg/g glucan) could readily reduce the cellulase (Celluclast 1.5 L®) loading by 8 times from 96.7 to 12.1 mg protein/g glucan and achieve a glucan EC of 80% at a hydrolysis time of 72 h. With the same cellulase (Celluclast 1.5 L®) loading (24.2 mg protein/g glucan), the ECs of glucan in LHW-pretreated bamboo, eucalyptus, and Masson pine substrates increased from 57%, 54% and 45% (without SP) to 87%, 94% and 86% (with 80 mg SP/g glucan), respectively. Similar effects were also observed when Cellic CTec2, a newer-generation cellulase preparation, was used. Mechanistic studies indicated that the adsorption of soluble SP onto the surface of lignin residues could reduce the nonproductive binding of cellulolytic enzymes to lignin. The cost of the SP required for effective promotion would be equivalent to the cost of 2.9 mg cellulase (Celluclast 1.5 L®) protein (or 1.2 FPU/g glucan), if a proposed semi-simultaneous saccharification and fermentation (semi-SSF) model was used.
CONCLUSIONS: Near-complete saccharification of glucan in LHW-pretreated lignocellulosic substrates could be achieved with the addition of the inexpensive and biocompatible SP additive extracted from DSP. This simple but remarkably effective technique could readily contribute to improving the economics of the cellulosic biorefinery industry.
RESULTS: Here, we firstly report that a soluble soy protein (SP) extracted from inexpensive defatted soy powder (DSP) showed excellent performance in promoting the EC of glucan in LHW-pretreated lignocellulosic substrates. The addition of the SP (80 mg/g glucan) could readily reduce the cellulase (Celluclast 1.5 L®) loading by 8 times from 96.7 to 12.1 mg protein/g glucan and achieve a glucan EC of 80% at a hydrolysis time of 72 h. With the same cellulase (Celluclast 1.5 L®) loading (24.2 mg protein/g glucan), the ECs of glucan in LHW-pretreated bamboo, eucalyptus, and Masson pine substrates increased from 57%, 54% and 45% (without SP) to 87%, 94% and 86% (with 80 mg SP/g glucan), respectively. Similar effects were also observed when Cellic CTec2, a newer-generation cellulase preparation, was used. Mechanistic studies indicated that the adsorption of soluble SP onto the surface of lignin residues could reduce the nonproductive binding of cellulolytic enzymes to lignin. The cost of the SP required for effective promotion would be equivalent to the cost of 2.9 mg cellulase (Celluclast 1.5 L®) protein (or 1.2 FPU/g glucan), if a proposed semi-simultaneous saccharification and fermentation (semi-SSF) model was used.
CONCLUSIONS: Near-complete saccharification of glucan in LHW-pretreated lignocellulosic substrates could be achieved with the addition of the inexpensive and biocompatible SP additive extracted from DSP. This simple but remarkably effective technique could readily contribute to improving the economics of the cellulosic biorefinery industry.
摘要：
背景:液体热水(LHW)预处理已被认为是用于促进木质纤维素通过生物转化转化为生物燃料的最工业上可行和环境友好的方法之一。然而,预处理水解产物中的木质素碎片优先彼此缩合，然后在苛刻的条件下沉积回纤维素表面。特别是,在高温LHW预处理条件下，木质素倾向于重新定位或重新分布。纤维素表面上的木质素残留物会导致纤维素分解酶的显著非生产性结合，并因此负面影响预处理底物中葡聚糖的酶促转化(EC)。虽然添加剂如牛血清白蛋白（BSA）和吐温系列已被用来减少非生产性结合的酶通过阻断木质素，这些添加剂的高成本或非生物相容性限制了它们在工业应用中的潜力。
结果：这里，我们首次报道了从廉价的脱脂大豆粉（DSP）中提取的可溶性大豆蛋白（SP）在LHW预处理的木质纤维素底物中显示出优异的促进葡聚糖EC的性能。添加SP（80mg/g葡聚糖）可以很容易地将纤维素酶（Celluclast1.5L®）负荷从96.7降低8倍至12.1mg蛋白质/g葡聚糖，并在水解时间为72小时时达到80％的葡聚糖EC。使用相同的纤维素酶（Celluclast1.5L®）负荷（24.2mg蛋白质/g葡聚糖），LHW预处理竹子中葡聚糖的ECs，桉树,马尾松基质从57%增加，54%和45%(无SP)到87%，94%和86%（含80mgSP/g葡聚糖），分别。当新一代纤维素酶制备物CellicCTec2时，也观察到类似的效果，被使用。机理研究表明，可溶性SP在木质素残留物表面的吸附可以减少纤维素分解酶与木质素的非生产性结合。有效推广所需的SP成本相当于2.9mg纤维素酶（Celluclast1.5L®）蛋白（或1.2FPU/g葡聚糖）的成本，如果使用拟议的半同时糖化和发酵（半SSF）模型。
结论:通过添加从DSP提取的廉价且生物相容的SP添加剂,可以实现LHW预处理的木质纤维素底物中葡聚糖的接近完全糖化。这种简单但非常有效的技术可以很容易地有助于改善纤维素生物炼制工业的经济性。
结果：这里，我们首次报道了从廉价的脱脂大豆粉（DSP）中提取的可溶性大豆蛋白（SP）在LHW预处理的木质纤维素底物中显示出优异的促进葡聚糖EC的性能。添加SP（80mg/g葡聚糖）可以很容易地将纤维素酶（Celluclast1.5L®）负荷从96.7降低8倍至12.1mg蛋白质/g葡聚糖，并在水解时间为72小时时达到80％的葡聚糖EC。使用相同的纤维素酶（Celluclast1.5L®）负荷（24.2mg蛋白质/g葡聚糖），LHW预处理竹子中葡聚糖的ECs，桉树,马尾松基质从57%增加，54%和45%(无SP)到87%，94%和86%（含80mgSP/g葡聚糖），分别。当新一代纤维素酶制备物CellicCTec2时，也观察到类似的效果，被使用。机理研究表明，可溶性SP在木质素残留物表面的吸附可以减少纤维素分解酶与木质素的非生产性结合。有效推广所需的SP成本相当于2.9mg纤维素酶（Celluclast1.5L®）蛋白（或1.2FPU/g葡聚糖）的成本，如果使用拟议的半同时糖化和发酵（半SSF）模型。
结论:通过添加从DSP提取的廉价且生物相容的SP添加剂,可以实现LHW预处理的木质纤维素底物中葡聚糖的接近完全糖化。这种简单但非常有效的技术可以很容易地有助于改善纤维素生物炼制工业的经济性。
