Efficient production of optically pure l-lactic acid from food waste at ambient temperature by regulating key enzyme activity

Abstract

Bio-production of optically pure L-lactic acid from food waste has attracted much interest as it can treat organic wastes with simultaneous recovery of valuable by-products. However, the yield of L-lactic acid was very low and no optically pure L-lactic acid was produced in the literature due to (1) the lower activity of enzymes involved in hydrolysis and L-lactic acid generation, and (2) the participation of other enzymes related to D-lactic acid and acetic and propionic acids production. In this paper, a new strategy was reported for effective production of optically pure L-lactic acid from food waste at ambient temperature, i.e. via regulating key enzyme activity by sewage sludge supplement and intermittent alkaline fermentation. It was found that not only optically pure L-lactic acid was produced, but the yield was enhanced by 2.89-fold. The mechanism study showed that the activities of enzymes relevant to food waste hydrolysis and lactic acid production were enhanced, and the key enzymes related to volatile fatty acids and D-lactic acid generations were severally decreased or inhibited. Also, the microbes responsible for L-lactic acid production were selectively proliferated. Finally, the pilot-scale continuous experiment was conducted to testify the feasibility of this new technique.

Food waste generation and industrial uses: A review

“…The production of biological metabolites to be used as renewable and biodegradable substitutes for petrochemical products is currently the focus of growing interest. These metabolites are: lactate for the production of polylactate, a plastic constituent; polyhydroxyalkanotes, particularly polyhydroxybutyrate, which are natural storage polymer of many bacterial species with properties similar to polyethylene and polypropylene; succinate, a valuable and flexible precursor for pharmaceutical, plastic and detergent production (Hassan et al, 2013;Sulaiman et al, 2014;Li et al, 2015). As for the biofuel production from virgin feedstocks, considerable debate surrounds the manufacture of bioplastics from natural materials, raising the issue as to whether they produce a negative impact on human food supply.…”

“…Bio-production of optically pure L-lactic acid from food waste has attracted considerable interest due to its ability to treat organic wastes with simultaneous recovery of valuable by-products (Li et al, 2015). A new strategy was reported for effective production of optically pure L-lactic acid from food waste at ambient temperature, regulating key enzyme activity by sewage sludge supplementation and intermittent alkaline fermentation.…”

“…A new strategy was reported for effective production of optically pure L-lactic acid from food waste at ambient temperature, regulating key enzyme activity by sewage sludge supplementation and intermittent alkaline fermentation. A production of optically pure L-lactic acid was achieved from food waste at ambient temperature with a yield of 0.52 g/gCOD (Li et al, 2015).…”

Increasing Profits in Food Waste Biorefinery—A Techno-Economic Analysis

“…Lactic acid and polylactic acid relevance in this assessment is expressed in that that technology has been commercialized and has demonstrated its sustainability and profitability [2]. The conversion of food-waste into lactic acid by uncontrolled pH mixed culture fermentation, has been shown to be feasible [28][29][30][31], achieving lactic acid concentrations of 30 g/L with lactic acid selectivity of 93% (in COD base) over other organic acids [29,32]. Lactic acid market price range, 1000-1600 USD/t [13,27,33,34], and its derivatives, i.e., poly-lactic acid and acrylic acid, 1600-2200 USD/t [27,33,35] makes them attractive alternatives to biogas.…”

Dynamic membrane-assisted fermentation of food wastes for enhancing lactic acid production

“…Carbohydrates were measured by the phenol-sulfuric method with glucose used as a standard. The elements in the food waste substrate were assayed by an elemental analyzer according to Li et al (2015). The bacterial enzymes in the fermentation broth were detected based on the methods described by Li et al (2015).…”