Integrated lactic acid production from lignocellulosic agricultural wastes under thermal conditions

Composition of Lignocellulose Hydrolysate in Different Biorefinery Strategies: Nutrients and Inhibitors

“…The lignocellulosic hydrolysates produced by on-site and off-site strategies are quite different for downstream fermentation. In off-site saccharification, free enzymes are used as catalysts for the saccharification process, so the nutrients and inhibitors in the hydrolysates mostly come from the lignocellulosic substrates themselves and pretreatment processes, while, in on-site saccharification, the hydrolysates are also a fermentation medium for enzyme-producing strains [40]; therefore, besides the nutrients and inhibitors from the substrates and pretreatment processes, metabolic products from the strains are also contained in hydrolysates, and both nutrients and potential inhibitors may be included for downstream fermentation [3]. The differences among lignocellulose hydrolysis in various saccharification approaches will be further discussed in the next section.…”

“…For example, Liu et al [26] successfully achieved the fermentation of pullulan using condensed CBS sugar liquor without any nutrient supplementation. Similarly, lactic acids were produced by directly inoculating lactic acid bacteria (LAB) strains into the CBS hydrolysates to initiate the fermentation process [3]. On the other hand, since the strains used in CBS are anaerobic Clostridium thermocellum [200], certain amounts of metabolic intermediates such as lactic acid and acetic acid are produced, which may inhibit some anaerobic fermentation processes for bioenergy production, such as acetone-butanol-ethanol (ABE) fermentation [157,201].…”

“…Lignocellulosic biomass (LCB), as one of the most abundant renewable resources in the world, plays an increasingly important role in the circular economy and sustainable development, thus attracting great attention in various research areas. These studies are dedicated to developing techniques in the bioconversion process known as biorefinery which converts lignocellulosic substrates into products such as biofuels, bioplastics, biobased chemicals, and bio-gases, to substitute non-renewable fossil-based fuels partially or completely [1][2][3][4]. The biorefinery processes of lignocellulosic biomass can be classified into two groups based on conversion approaches and intermediate products (platform molecules).…”

De Novo Multienzyme Synthetic Pathways for Lactic Acid Production

“…44 However, this process suffers from long pathways (10−11 steps from glucose to LA via the Embden−Meyerhof−Parnas pathway), and the main starting materials used are still hexose sugars (glucose and sucrose) and lignocellulosic feedstocks, which compete with human food production and are associated with additional biomass pretreatment costs. 45,46 Recently, a chemoenzymatic synthesis of LA from C1 formaldehyde was reported by integrating formolase (FLS)-catalyzed formaldehyde condensation with NaOH-mediated dihydroxyacetone (DHA) rearrangement in two steps. 47 However, only racemic LA was synthesized, and an additional chiral resolution step was required.…”

“…The chemocatalytic platforms for LA production from biomass-derived carbohydrates demand toxic and high-cost metal catalysts, such as Pb­(II) and Al­(III)–Sn­(II), and severe reaction conditions (up to 453 K). , Nowadays, over 90% of commercialized LA is produced by microbial fermentation with high optical purity . However, this process suffers from long pathways (10–11 steps from glucose to LA via the Embden–Meyerhof–Parnas pathway), and the main starting materials used are still hexose sugars (glucose and sucrose) and lignocellulosic feedstocks, which compete with human food production and are associated with additional biomass pretreatment costs. , Recently, a chemoenzymatic synthesis of LA from C1 formaldehyde was reported by integrating formolase (FLS)-catalyzed formaldehyde condensation with NaOH-mediated dihydroxyacetone (DHA) rearrangement in two steps . However, only racemic LA was synthesized, and an additional chiral resolution step was required.…”