Tang Chaojun, Cavka Adnan, Bui Mai, Jönsson Leif J
Department of Chemistry, Umeå University, Umeå, Sweden.
Sekab, Örnsköldsvik, Sweden.
Front Bioeng Biotechnol. 2024 Jul 11;12:1419723. doi: 10.3389/fbioe.2024.1419723. eCollection 2024.
Enzymatic saccharification is used to convert polysaccharides in lignocellulosic biomass to sugars which are then converted to ethanol or other bio-based fermentation products. The efficacy of commercial cellulase preparations can potentially increase if lytic polysaccharide monooxygenase (LPMO) is included. However, as LPMO requires both a reductant and an oxidant, such as molecular oxygen, a reevaluation of process configurations and conditions is warranted. Saccharification and fermentation of pretreated softwood was investigated in demonstration-scale experiments with 10 m bioreactors using an LPMO-containing cellulase preparation, a xylose-utilizing yeast, and either simultaneous saccharification and fermentation (SSF) or hybrid hydrolysis and fermentation (HHF) with a 24-hour or 48-hour initial phase and with 0.15 vvm aeration before addition of the yeast. The conditions used for HHF, especially with 48 h initial phase, resulted in better glucan conversion, but in poorer ethanol productivity and in poorer initial ethanol yield on consumed sugars than the SSF. In the SSF, hexose sugars such as glucose and mannose were consumed faster than xylose, but, in the end of the fermentation >90% of the xylose had been consumed. Chemical analysis of inhibitory pretreatment by-products indicated that the concentrations of heteroaromatic aldehydes (such as furfural), aromatic aldehydes, and an aromatic ketone decreased as a consequence of the aeration. This was attributed mainly to evaporation caused by the gas flow. The results indicate that further research is needed to fully exploit the advantages of LPMO without compromising fermentation conditions.
酶促糖化用于将木质纤维素生物质中的多糖转化为糖，然后将这些糖转化为乙醇或其他生物基发酵产品。如果加入裂解多糖单加氧酶（LPMO），商业纤维素酶制剂的功效可能会提高。然而，由于LPMO既需要还原剂又需要氧化剂，如分子氧，因此有必要重新评估工艺配置和条件。在使用含LPMO的纤维素酶制剂、利用木糖的酵母以及同步糖化发酵（SSF）或混合水解发酵（HHF）的示范规模实验中，使用10米生物反应器对预处理软木的糖化和发酵进行了研究，初始阶段为24小时或48小时，并在添加酵母前以0.15 vvm的通气量进行通气。HHF所用的条件，尤其是初始阶段为48小时的情况，导致葡聚糖转化率更高，但与SSF相比，乙醇生产率更低，消耗糖的初始乙醇产率也更低。在SSF中，葡萄糖和甘露糖等己糖的消耗速度比木糖快，但在发酵结束时，>90%的木糖已被消耗。对抑制性预处理副产物的化学分析表明，由于通气，杂芳族醛（如糠醛）、芳族醛和芳族酮的浓度降低。这主要归因于气流引起的蒸发。结果表明，需要进一步研究以充分利用LPMO的优势而不影响发酵条件。
