Tarraran Loredana, Mazzoli Roberto
Structural and Functional Biochemistry, Laboratory of Proteomics and Metabolic Engineering of Prokaryotes, Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123 Torino, Italy.
FEMS Microbiol Lett. 2018 Aug 1;365(15). doi: 10.1093/femsle/fny126.
Lactic acid bacteria (LAB) have a long history in industrial processes as food starters and biocontrol agents, and also as producers of high-value compounds. Lactic acid, their main product, is among the most requested chemicals because of its multiple applications, including the synthesis of biodegradable plastic polymers. Moreover, LAB are attractive candidates for the production of ethanol, polyhydroalkanoates, sweeteners and exopolysaccharides. LAB generally have complex nutritional requirements. Furthermore, they cannot directly ferment inexpensive feedstocks such as lignocellulose. This significantly increases the cost of LAB fermentation and hinders its application in the production of high volumes of low-cost chemicals. Different strategies have been explored to extend LAB fermentation to lignocellulosic biomass. Fermentation of lignocellulose hydrolysates by LAB has been frequently reported and is the most mature technology. However, current economic constraints of this strategy have driven research for alternative approaches. Co-cultivation of LAB with native cellulolytic microorganisms may reduce the high cost of exogenous cellulase supplementation. Special attention is given in this review to the construction of recombinant cellulolytic LAB by metabolic engineering, which may generate strains able to directly ferment plant biomass. The state of the art of these strategies is illustrated along with perspectives of their applications to industrial second generation biorefinery processes.
乳酸菌（LAB）在工业生产中作为食品发酵剂、生物防治剂以及高价值化合物的生产者有着悠久的历史。乳酸是它们的主要产物，由于其多种应用，包括可生物降解塑料聚合物的合成，是最受欢迎的化学品之一。此外，乳酸菌是生产乙醇、聚羟基脂肪酸酯、甜味剂和胞外多糖的有吸引力的候选者。乳酸菌通常有复杂的营养需求。此外，它们不能直接发酵木质纤维素等廉价原料。这显著增加了乳酸菌发酵的成本，并阻碍了其在大量低成本化学品生产中的应用。人们探索了不同的策略来将乳酸菌发酵扩展到木质纤维素生物质。乳酸菌对木质纤维素水解产物的发酵已有频繁报道，且是最成熟的技术。然而，该策略当前的经济限制推动了对替代方法的研究。将乳酸菌与天然纤维素分解微生物共培养可能会降低补充外源纤维素酶的高成本。本综述特别关注通过代谢工程构建重组纤维素分解乳酸菌，这可能产生能够直接发酵植物生物质的菌株。阐述了这些策略的现状以及它们应用于工业第二代生物精炼过程的前景。
