Biotechnological advances in lactic acid production by lactic acid bacteria: lignocellulose as novel substrate

The production of high added-value products from lignocellulose is proposed as a suitable alternative to petroleum-based resources in terms of environmental preservation, sustainability, and circular economy. Lactic acid is a versatile building block that can be produced via fermentative routes by several groups of microorganisms, including yeasts and microalgae, which are bacteria recognized to achieve the highest concentrations. Lactic acid, among other substances, can be used as a starting point in the production of poly-lactic acid, which is a biopolymer with many applications due to its resistance, durability, biodegradability, and biocompatibility. Lactic acid production can be performed from lignocellulosic biomass. However, lactic acid production from lignocellulose faces several hurdles such as carbohydrate hydrolysis to release sugars, the co-utilization of sugar mixtures by the fermenting microorganism, and the presence of degradation compounds released during pretreatment. In this review, a general overview of lactic-acid bacterial fermentation from lignocellulose is provided, starting from the potential substrates and their composition, the different metabolic pathways involved, and the purification steps. The main challenges are discussed and the newest approaches to solve the limitations of the process are proposed. (C) 2018 Society of Chemical Industry and John Wiley & Sons, Ltd