Aulitto Martina, Fusco Salvatore, Nickel David Benjamin, Bartolucci Simonetta, Contursi Patrizia, Franzén Carl Johan
1Department of Biology, University of Naples Federico II, 80126 Naples, Italy.
2Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
Biotechnol Biofuels. 2019 Feb 28;12:45. doi: 10.1186/s13068-019-1382-2. eCollection 2019.
Lignocellulosic biomass is an abundant and sustainable feedstock, which represents a promising raw material for the production of lactic acid via microbial fermentation. However, toxic compounds that affect microbial growth and metabolism are released from the biomass upon thermochemical pre-treatment. So far, susceptibility of bacterial strains to biomass-derived inhibitors still represents a major barrier to lactic acid production from lignocellulose. Detoxification of the pre-treated lignocellulosic material by water washing is commonly performed to alleviate growth inhibition of the production microorganism and achieve higher production rates.
In this study, we assessed the feasibility of replacing the washing step with integrated cellular adaptation during pre-culture of MA-13 prior to simultaneous saccharification and lactic acid fermentation of steam exploded wheat straw. Using a seed culture pre-exposed to 30% hydrolysate led to 50% shorter process time, 50% higher average volumetric and 115% higher average specific productivity than when using cells from a hydrolysate-free seed culture.
Pre-exposure of MA-13 to hydrolysate supports adaptation to the actual production medium. This strategy leads to lower process water requirements and combines cost-effective seed cultivation with physiological pre-adaptation of the production strain, resulting in reduced lactic acid production costs.
木质纤维素生物质是一种丰富且可持续的原料，是通过微生物发酵生产乳酸的有前景的原材料。然而，热化学预处理会使生物质释放出影响微生物生长和代谢的有毒化合物。到目前为止，细菌菌株对生物质衍生抑制剂的敏感性仍然是木质纤维素生产乳酸的主要障碍。通常通过水洗对预处理的木质纤维素材料进行解毒，以减轻生产微生物的生长抑制并实现更高的生产率。
在本研究中，我们评估了在对蒸汽爆破麦草进行同步糖化和乳酸发酵之前，在MA-13预培养过程中用整合细胞适应性替代洗涤步骤的可行性。与使用无水解产物种子培养物中的细胞相比，使用预先暴露于30%水解产物的种子培养物可使工艺时间缩短50%，平均体积产率提高50%，平均比生产率提高115%。
MA-13预先暴露于水解产物有助于其适应实际生产培养基。该策略可降低工艺用水需求，并将具有成本效益的种子培养与生产菌株的生理预适应相结合，从而降低乳酸生产成本。
