Lin Chien-Yuan, Geiselman Gina M, Liu Di, Magurudeniya Harsha D, Rodriguez Alberto, Chen Yi-Chun, Pidatala Venkataramana, Unda Faride, Amer Bashar, Baidoo Edward E K, Mansfield Shawn D, Simmons Blake A, Singh Seema, Scheller Henrik V, Gladden John M, Eudes Aymerick
DOE Joint BioEnergy Institute, Emeryville, CA, 94608, USA.
Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Biotechnol Biofuels Bioprod. 2022 Dec 25;15(1):145. doi: 10.1186/s13068-022-02245-4.
Lignocellulosic resources are promising feedstocks for the manufacture of bio-based products and bioenergy. However, the inherent recalcitrance of biomass to conversion into simple sugars currently hinders the deployment of advanced bioproducts at large scale. Lignin is a primary contributor to biomass recalcitrance as it protects cell wall polysaccharides from degradation and can inhibit hydrolytic enzymes via non-productive adsorption. Several engineering strategies have been designed to reduce lignin or modify its monomeric composition. For example, expression of bacterial 3-dehydroshikimate dehydratase (QsuB) in poplar trees resulted in a reduction in lignin due to redirection of metabolic flux toward 3,4-dihydroxybenzoate at the expense of lignin. This reduction was accompanied with remarkable changes in the pools of aromatic compounds that accumulate in the biomass.
The impact of these modifications on downstream biomass deconstruction and conversion into advanced bioproducts was evaluated in the current study. Using ionic liquid pretreatment followed by enzymatic saccharification, biomass from engineered trees released more glucose and xylose compared to wild-type control trees under optimum conditions. Fermentation of the resulting hydrolysates using Rhodosporidium toruloides strains engineered to produce α-bisabolene, epi-isozizaene, and fatty alcohols showed no negative impact on cell growth and yielded higher titers of bioproducts (as much as + 58%) in the case of QsuB transgenics trees.
Our data show that low-recalcitrant poplar biomass obtained with the QsuB technology has the potential to improve the production of advanced bioproducts.
木质纤维素资源是制造生物基产品和生物能源的理想原料。然而，生物质转化为单糖的固有抗性目前阻碍了先进生物产品的大规模应用。木质素是生物质抗性的主要贡献者，因为它保护细胞壁多糖不被降解，并可通过非生产性吸附抑制水解酶。已经设计了几种工程策略来减少木质素或改变其单体组成。例如，杨树中细菌3-脱氢莽草酸脱水酶（QsuB）的表达导致木质素减少，这是由于代谢通量转向3,4-二羟基苯甲酸，以木质素为代价。这种减少伴随着生物质中积累的芳香族化合物库的显著变化。
在本研究中评估了这些修饰对下游生物质解构和转化为先进生物产品的影响。在最佳条件下，与野生型对照树相比，使用离子液体预处理然后进行酶糖化，工程树的生物质释放出更多的葡萄糖和木糖。使用经过工程改造以生产α-红没药烯、表异紫穗槐烯和脂肪醇的红酵母菌株对所得水解产物进行发酵，对细胞生长没有负面影响，并且在QsuB转基因树的情况下，生物产品的滴度更高（高达+58%）。
我们的数据表明，通过QsuB技术获得的低抗性杨树生物质具有提高先进生物产品产量的潜力。
