L-lactic Acid Production Research Articles

Plant Proteins as an Alternative Nitrogen Source for Chiral Purity L-Lactic Acid Fermentation from Lignocellulose Feedstock

High optical purity lactic acid is in high demand as the precursor for synthesizing polylactic acid (PLA). The costs of expensive carbohydrates and nitrogen source materials accounts for a large portion of the production costs in lactic homo-fermentation. The use of lignocellulosic biomass for lactic acid production reduces the cost of the carbohydrate feedstock, but the cost of nitrogen sources is a big challenge when considering the high prices of general nitrogen sources. Low-cost nitrogen materials are vulnerable to being contaminated by exogenous mixed L-lactic acid and D-lactic acid; thus, their feasibility as nitrogen sources for the production of optically pure lactic acid products is hindered. The available reports focus on cost reduction using agro-industrial byproducts as nutrient sources, with these presenting fewer concerns on the effect of the optical purity of lactic acid-product monomers for polymerization. In this study, commonly used low-cost nutrient sources were characterized and screened for high optical purity L-lactic acid fermentation. Corn steep liquor (CSL), a widely used and cheap nutrient for lactic acid fermentation, was found not to be suitable because of its high content of mixed D-/L-lactic acids (up to 20%, w/w). On the other hand, cottonseed meal was found to be completely free of mixed L-/D-lactic acids. Therefore, the cottonseed meal was hydrolyzed with dilute sulfuric acid and used as a nitrogen source for L-lactic acid fermentation using lignocellulose feedstock as a substitution for yeast extract and peptone. The results showed that the final L-lactic acid titer reached 96.5 ± 0.2 g/L from 25% (w/w)-solids loaded pretreated and biodetoxified wheat straw with a yield of 0.31 g/g feedstock and an optical purity of 99.7%. The techno-economic evaluation indicated that the cost of the cottonseed meal was only USD 0.193/kg of lactic acid product, and the minimum lactic acid selling price (MLSP) was USD 0.813/kg of lactic acid product, which was only 25.1% compared to the use of yeast extract and peptone as the nutrients. Cellulosic L-lactic acid production using cottonseed meal as a complex nutrient source showed competitive performance when compared to starch feedstock from food crops.

Ultrasonic‑assisted molten salt hydrates pretreated Eucheuma cottonii residues as a greener precursor for third-generation l-lactic acid production

This study aims to establish an efficient pretreatment method that facilitates the conversion of sugars from macroalgae wastes, Eucheuma cottonii residues (ECRs) during hydrolysis and subsequently enhances l-lactic acid (L-LA) production. Hence, ultrasonic-assisted molten salt hydrates (UMSHs) pretreatment was proposed to enhance the accessibility of ECRs to hydrolyze into glucose through dilute acid hydrolysis (DAH). The obtained hydrolysates were employed as the substrate in producing L-LA by separate hydrolysis and fermentation (SHF). The maximum glucose yield (97.75 %) was achieved using UMSHs pretreated ECRs with 40 wt% ZnCl2 at 80 °C for 2 h and followed with DAH. The optimum glucose to L-LA yield obtained for SHF was 90.08 % using 5 % (w/w) inoculum cell densities of B. coagulans ATCC 7050 with yeast extract (YE). A comparable performance (89.65 %) was obtained using a nutrient combination (lipid-extracted Chlorella vulgaris residues (CVRs), vitamin B3, and vitamin B5) as a partial alternative for YE.

Production of biopolymer precursors beta-alanine and L-lactic acid from CO2 with metabolically versatile Rhodococcus opacus DSM 43205.

Hydrogen oxidizing autotrophic bacteria are promising hosts for conversion of CO2 into chemicals. In this work, we engineered the metabolically versatile lithoautotrophic bacterium R. opacus strain DSM 43205 for synthesis of polymer precursors. Aspartate decarboxylase (panD) or lactate dehydrogenase (ldh) were expressed for beta-alanine or L-lactic acid production, respectively. The heterotrophic cultivations on glucose produced 25 mg L−1 beta-alanine and 742 mg L−1 L-lactic acid, while autotrophic cultivations with CO2, H2, and O2 resulted in the production of 1.8 mg L−1 beta-alanine and 146 mg L−1 L-lactic acid. Beta-alanine was also produced at 345 μg L−1 from CO2 in electrobioreactors, where H2 and O2 were provided by water electrolysis. This work demonstrates that R. opacus DSM 43205 can be engineered to produce chemicals from CO2 and provides a base for its further metabolic engineering.

Optimisation of pre-harvest sago frond sap for the production of l-lactic acid using Lactococcus lactis IO-1

The major restriction of sago palm plantation is the long maturation period for the starch extraction. As such, alternative commodity has to be identified to increase commercial value of sago palm especially from the by-product. Sago frond has been harvested to have numerous advantages as an alternative substrate for the production of biomaterial and biofuel such as lactic acid and bioethanol. This study focuses on effective approach to maximise the concentration of sugar in the substrate and to identify the ideal concentration of sago frond sap (SFSp) as sole media to produce l-lactic acid and grow L. lactis IO-1. Result shows that SFSp extracted from sago rachis using a roller press machine contained glucose (43.8 g/L), xylose (17.3 g/L) as free sugars and starch (5.55 g/L). Combination of enzymatic hydrolysis and sterilisation pre-treatment was found to maximise the concentration of total carbon source (68 g/L) and sterilised sago frond sap suitable to be used for fermentation process. The ideal concentration of SFSp that was determined at 50% dilution produces the highest amount of l-lactic acid (24.02 g/L) synergist by most efficient sugar consumption (89.93%). The use of SFSp as fermentation medium for l-lactic acid production generated maximum biomass concentration of 14.53 g/L. The utilisation of SFSp extracted from pre-harvest sago frond as substrate promote efficiency of l-lactic acid production associated to exceptional growth performance of L. lactis IO-1. In conclusion, the concept of utilizing by-product from sago palm as novel raw material promise reliable resources and superiority of L. lactis IO-1 to metabolise sugar in SFSp promote lucrative and ethical production of l-lactic acid.

Engineered Microbial Cell Factories for Sustainable Production of L-Lactic Acid: A Critical Review

With the increasing demand for the biodegradable polymer material polylactic acid and its advantage of being metabolized by the human body, L-lactic acid (L-LA) is becoming increasingly attractive in environmental protection and food industry applications. However, the supply of L-LA is not satisfied, and the price is still high. Compared to enzymatic and chemical synthesis methods, L-LA production by microbial fermentation has the advantages of low cost, large yield, simple operation, and environmental protection. This review summarizes the advances in engineering microbial cell factories to produce L-LA. First, the synthetic pathways and microorganisms for L-LA production are outlined. Then, the metabolic engineering strategies for constructing cell factories to overproduce L-LA are summarized and fermentation modes for L-LA production are also given. Finally, the challenges and prospects of the microbial production of L-LA are discussed. This review provides theoretical guidance for researchers engaged in L-LA production.

MgO recycling in l-lactic acid fermentation and effects of the reusable alkaline neutralizer on Lactobacillus rhamnosus: From process integration to transcriptome analysis

l-lactic acid fermentation coupled with MgO recycling was investigated. Factors affecting yield in MgCl2 pyrolysis were optimized by Box-Behnken design with a conversion rate of 97.35%, and recycled MgO was characterized by TG-DSC and XRD analyses. Specific surface area and average pore size of the recycled MgO were increased by 21.18% and 37.74%, respectively, and the mean particle size of the recycled MgO (6696.7 nm) was smaller than that of the pure MgO (7086.7 nm). The spontaneously formed honeycomb structure which could promote l-lactic acid fermentation was demonstrated, and MgO was recycled for 5 times providing stable titer (141.21–144.25 g/L), yield (94.51–95.26%) and productivity (2.03–2.09 g/L/h) with high cell viability (109.55 CFU/mL). Influence of the recyclable MgO on Lactobacillus rhamnosus LA-04-1 (L. rhamnosus LA-04-1) was further revealed, and 62 related genes involved in 13 key pathways were located by transcriptome analysis. This study provides a potential way for environmental-friendly production of l-lactic acid by decreasing waste discharge and energy consumption.

Enhanced lactic acid production with indigenous microbiota from date pulp waste and keratin protein hydrolysate from chicken feather waste

A substantial amount of keratin, a key protein with excellent material-forming properties, can be sustainably extracted from chicken feathers, which are commonly discarded in the poultry industry. The keratin protein found in chicken feathers can serve as a nitrogen source and a pH regulator for microbes. In this study, the use of indigenous bacteria and extracted keratin protein hydrolysate from chicken feathers as a nitrogen source improved lactic acid production from date pulp waste by fermentation. After six days of optimal dark fermentation time at pH 6, the maximum concentration of L-lactic acid (46.2 g/L) was obtained with keratin protein hydrolysate and date pulp waste substrate. Under the same conditions, the value was 2.12 times higher than that of the date pulp waste substrate (21.7 g/L) without the addition of keratin protein hydrolysate. Under optimal conditions, volumetric lactic acid productivity and yield were 7.7 g/L/day and 0.3 g/g substrate, respectively. Keratin protein hydrolysate proved to be the most effective neutralizing agent for L-lactic acid production at a concentration of 6 g/L. The combination of keratin protein hydrolysate and date pulp waste was studied for the first time as a substrate for lactic acid production. Keratin protein hydrolysate was found to buffer pH changes during fermentation. Poultry and plant by-products are usually available in agriculturally challenged areas. Therefore, this study provides an excellent opportunity to recycle waste and improve the overall circular economy of such agro-industrial complexes.

Biomodulation of Physicochemical Parameters, Aromas, and Sensory Profile of Craft Beers by Using Non-Saccharomyces Yeasts.

Beer is an alcoholic beverage produced by the metabolism of yeasts and made from water, malt, and hops. In recent years, the interest in craft beers has increased considerably due to the demand for new beverages and the consumer’s willingness to pay higher prices. This article explores the sensorial changes produced in craft beers by using different Saccharomyces and non-Saccharomyces yeasts with several instrumental and sensory analyses performed. After a primary fermentation process with Saccharomyces cerevisiae or Lachancea thermotolerans, it was observed that green beer brewed with L. thermotolerans had a lower pH (3.41) due to the significant production of l-lactic acid (3.98 g/L) compared to that brewed with S. cerevisiae. Following, the bottle conditioning was carried out with a culture of S. cerevisiae, L. thermotolerans, Hanseniaspora vineae, or Schizosaccharomyces pombe. Of note is the increased production of aromatic esters, including 2-phenylethyl acetate in the H. vineae conditioning, which is associated with a high aromatic quality, as well as ethyl lactate in all samples, whose main fermentation was carried out with L. thermotolerans. Although this research is at an early stage, future complementary studies may shed more light on this topic.

Production of L-Lactic Acid in Saccharomyces cerevisiae Through Metabolic Engineering and Rational Cofactor Engineering

Production of L-Lactic Acid in Saccharomyces cerevisiae Through Metabolic Engineering and Rational Cofactor Engineering

Direct conversion of cellulose to l-lactic acid by a novel thermophilic Caldicellulosiruptor strain

BackgroundConsolidated bioprocessing (CBP) of lignocellulosic biomass to l-lactic acid using thermophilic cellulolytic/hemicellulolytic bacteria provides a promising solution for efficient lignocellulose conversion without the need for additional cellulolytic/hemicellulolytic enzymes. Most studies on the mesophilic and thermophilic CBP of lignocellulose to lactic acid concentrate on cultivation of non-cellulolytic mesophilic and thermophilic bacteria at temperatures of 30–55 °C with external addition of cellulases/hemicellulases for saccharification of substrates.Resultsl-Lactic acid was generated by fermenting microcrystalline cellulose or lignocellulosic substrates with a novel thermophilic anaerobic bacterium Caldicellulosiruptor sp. DIB 104C without adding externally produced cellulolytic/hemicellulolytic enzymes. Selection of this novel bacterium strain for lactic acid production is described as well as the adaptive evolution towards increasing the l-lactic acid concentration from 6 to 70 g/l on microcrystalline cellulose. The evolved strains grown on microcrystalline cellulose show a maximum lactic acid production rate of 1.0 g/l*h and a lactic acid ratio in the total organic fermentation products of 96 wt%. The enantiomeric purity of the l-lactic acid generated is 99.4%. In addition, the lactic acid production by these strains on several other types of cellulose and lignocellulosic feedstocks is also reported.ConclusionsThe evolved strains originating from Caldicellulosiruptor sp. DIB 104C were capable of producing unexpectedly large amounts of l-lactic acid from microcrystalline cellulose in fermenters. These strains produce l-lactic acid also from lignocellulosic feedstocks and thus represent an ideal starting point for development of a highly integrated commercial l-lactic acid production process from such feedstocks.

Cyclic l-lactide synthesis from lignocellulose biomass by biorefining with complete inhibitor removal and highly simultaneous sugars assimilation.

Cyclic chiral lactide is the monomer chemical for polymerization of high molecular weight polylactic acid (PLA). The synthesis of cyclic l-lactide starts from poly-condensation of l-lactic acid to a low molecular weight prepolymer and then depolymerized to cyclic l-lactide. Lignocellulose biomass is the most promising carbohydrate feedstock for lactic acid production, but the synthesis of cyclic l-lactide from l-lactic acid produced from lignocellulose has so far not been successful. The major barriers are the impurities of residual sugars and inhibitors in the crude cellulosic l-lactic acid product. Here we show a successful cyclic l-lactide synthesis from cellulosic l-lactic acid by lignocellulose biorefining with complete inhibitor removal and coordinated sugars assimilation. The removal of inhibitors from lignocellulose pretreatment was accomplished by biodetoxification using a unique fungus Amorphotheca resinae ZN1. The nonglucose sugars were completely and simultaneously assimilated at the same rate with glucose by the engineered l-lactic acid bacterium Pediococcus acidilactici. The l-lactic acid production from wheat straw was comparable to that from corn starch with high optical pure (99.6%), high l-lactic acid titer (129.4 g/L), minor residual total sugars (~2.2 g/L), and inhibitors free. The cyclic l-lactide was successfully synthesized from the regularly purified l-lactic acid and verified by detailed characterizations. This study paves the technical foundation of carbon-neutral production of biodegradable PLA from lignocellulose biomass.

Increasing Acid Tolerance of an Engineered Lactic Acid Bacterium Pediococcus acidilactici for L-Lactic Acid Production

Acid tolerance of the lactic acid bacterium (LAB) is crucially important for the production of free lactic acid as a chemical monomer by simplified purification steps. This study conducts both metabolic modification and adaptive evolution approaches on increasing the acid tolerance of an engineered Pediococcus acidilactici strain. The overexpression of the genes encoding lactate dehydrogenase, recombinase, chaperone, glutathione and ATPase did not show the observable changes in acid tolerance. On the other hand, the low pH adaptive evolution showed clear improvement. The L-lactic acid generation and cell viability of the adaptively evolved P. acidilactici were doubled at low pH up to 4.0 when wheat straw was used as carbohydrate feedstock. However, the further decrease in pH value close to the pKa (3.86) of lactic acid led to a dramatic reduction in L-lactic acid generation. This result shows a partially successful approach on improving the acid tolerance of the lactic acid bacterium P. acidilactici.

Evaluation of fresh water lactic acid bacteria for production of optically pure L-(+)-lactic acid

Background and objective Lactic acid bacteria (LAB) are generous producers of many industrially important products. Of these products, optically pure lactic acid is of great value as it is essential for production of highly crystalline poly-lactic acid, which is the most widely used biodegradable synthetic polymer. Hence, this study aimed to screen for thermotolerant LAB from a new source, which is fresh water samples collected from the coast of the Nile River, Egypt, and then evaluate their ability to produce optically pure L-lactic acid.Materials and methods LAB strains were isolated at 50°C and evaluated for producing optically pure L-lactic acid using high-performance liquid chromatography and BF-5. Effects of medium containing different sugar sources, incubation temperature, and initial pH of the medium on the purity and productivity of L-lactic acid were also studied.Results and discussion All obtained isolates were capable of producing optically pure L-lactic acid on different sugar sources. Changing the incubation temperature to 30°C positively affected both productivity and optical purity, which reached 5.0 g/l of 100% optically pure L-lactic acid. On the contrary, pH of the medium was confirmed to be also one of the major factors affecting productivity and optical purity of obtained L-lactic acid. For our isolates, pH 7.0 was the optimum one for the production process. The four promising producers of 100% optically pure L-lactic acid were molecularly identified as Lactiplantibacillus sp.Conclusion This is the first study describing the evaluation of the ability of fresh water LAB isolated from the Nile River to produce optically pure L-lactic acid.

Third-generation bioethanol and L-lactic acid production from red macroalgae cellulosic residue: Prospects of Industry 5.0 algae

The biorefinery approach for large-scale biomass utilization involving the co-production of bioethanol and value-added products has received a great deal of attention. A techno-economic evaluation of an innovative integrated biorefinery approach using macroalgae cellulosic residue (MCR) was investigated in the present study for the co-production of bioethanol and L-lactic acid (LLA) via Aspen Plus V10. The simulation resulted in a production capacity capable of producing 3856.8 kg/hr of anhydrous bioethanol, 6488.04 kg/hr of LLA, 4479.48 kg/hr of fertilizer, and 5233.79 kWh of electricity generation from a feedstock of 15883.3 kg/hr of MCR. The yield of products per unit mass of feedstock were 0.24 kg of anhydrous ethanol, 0.41 kg of LLA and 0.28 kg of fertilizer per kg of MCR. The bioethanol product has a purity of 99.7 wt%, while the product purity of LLA is 92.8 wt%. The electricity generated from the combined heat and power (CHP) plant managed to supply up to 70% of the plant's total electricity requirement. The implementation of Heat Exchanger Network (HEN) synthesis successfully generated a total energy savings of 35% through the optimization process. With a plant service year of 20 years, the payback period is 6.25 years, having a Return on investment (ROI) of 30.8%. Furthermore, the plant is equipped with futuristics integration of Industry 5.0, implementing the effort of human-robot interaction to achieve maximum efficiency and productivity.

HIGH LACTIC ACID PRODUCTION BY Lactobacillus sp. V156 ISOLATED FROM VIETNAMESE FERMENTED MUSTARD GREEN

In the present study, a lactic acid producing bacterium was isolated and screened from fermented mustard green. The selected bacterial strain (V156) was classified into genus Lactobacillus. High lactic acid concentration of 101.6 g/L and productivity of 2.82 g/L/h were efficiently achieved by Lactobacillus sp. V156 after 36 h of cultivation in fed-batch fermentation using ammonium hydroxide as the neutralizing agent. The production of high lactic acid in short cultivation time demonstrates that Lactobacillus sp. V156 is a promising strain for L-lactic acid production

Temperature shift and feeding strategies for improving l-lactic acid production by Lactiplantibacillus plantarum in batch and fed-batch cultures

The optimal culture conditions for l-lactic acid production by Lactiplantibacillus plantarum TBRC 9667 were investigated. The suboptimal initial pH and initial temperature (for upshift to 30 °C after 5 h) were first determined in shake-flask cultures to be pH 5.5 and 25 °C, respectively. The three process variables analysis (initial temperature of 25 °C or 30 °C, temperature upshift to 30 °C or 35 °C, and temperature shift point at 3 or 5 h) revealed a 25 °C – 35 °C temperature shift after 3 h to be the most suitable conditions for l-lactic acid production in batch cultures at controlled pH 5.5. Fed-batch experiments were further conducted in 2-L bioreactors using different glucose concentrations (20 and 40 g/L) and feed rates (calculated with a feed-rate equation based on an off-line Markov chain algorithm), with an initial feed rate of 0.3 L/h. A 25 °C – 35 °C temperature shift after 3 h, with 20 g/L glucose feeding after 9 h using an exponent of 0.025 for feed-rate, gave a 1.5-fold improvement over the suboptimal batch culture. The results highlight the potential of integrated temperature shift and off-line feeding strategies for improving l-lactic acid production.

L-Lactic Acid Production Using Engineered Saccharomyces cerevisiae with Improved Organic Acid Tolerance.

Lactic acid is mainly used to produce bio-based, bio-degradable polylactic acid. For industrial production of lactic acid, engineered Saccharomyces cerevisiae can be used. To avoid cellular toxicity caused by lactic acid accumulation, pH-neutralizing agents are used, leading to increased production costs. In this study, lactic acid-producing S. cerevisiae BK01 was developed with improved lactic acid tolerance through adaptive laboratory evolution (ALE) on 8% lactic acid. The genetic basis of BK01 could not be determined, suggesting complex mechanisms associated with lactic acid tolerance. However, BK01 had distinctive metabolomic traits clearly separated from the parental strain, and lactic acid production was improved by 17% (from 102 g/L to 119 g/L). To the best of our knowledge, this is the highest lactic acid titer produced by engineered S. cerevisiae without the use of pH neutralizers. Moreover, cellulosic lactic acid production by BK01 was demonstrated using acetate-rich buckwheat husk hydrolysates. Particularly, BK01 revealed improved tolerance against acetic acid of the hydrolysates, a major fermentation inhibitor of lignocellulosic biomass. In short, ALE with a high concentration of lactic acid improved lactic acid production as well as acetic acid tolerance of BK01, suggesting a potential for economically viable cellulosic lactic acid production.

Effects of different lignocellulosic wastes on alleviating acidification of L-lactic acid production from food waste fermentation

In this study, the effects of different lignocellulosic wastes on alleviating acidification in the fermentation of lactic acid (LA) from food waste (FW) were studied. Amongst three lignocellulosic wastes, spent mushroom substance (SMS) could reach 95.22% lignin removal efficiency through simple NaOH pretreatment. Results showed pretreated SMS was best choice for FW co-fermentation, the maximum LA concentration could reach 46.12 g/L. And the NaOH solution as neutraliser could save 5.69 mL compared with the other two lignocellulosic wastes. The reason for alleviating acidification was 4.71% calcium salt in SMS and the porous structure of SMS. Then, 50% of pretreated liquid (PL) produced in SMS pretreatment was reused in the co-fermentation process. Compared with the group with 0% PL loading, that with 50% PL loading showed an increase in LA concentration and optical purity of L-LA, reaching 50.95 g/L and 96.28%, and NaOH consumption also further decreased by 24.65%.

Meta-fermentation system with a mixed culture for the production of optically pure l-lactic acid can be reconstructed using the minimum isolates with a simplified pH control strategy.

Meta-l-lactic acid fermentation from non-treated kitchen refuse was reconstructed using a combination of isolated bacterial strains under several pH control strategies. The meta-fermentation system was successfully reconstructed using a combination of Weizmannia coagulans MN-07, Caldibacillus thermoamylovorans OM55-6, and Caldibacillus hisashii N-11 strains. Additionally, a simplified constant pH control strategy was employed, which decreased fermentation time and increased production. The optimum pH (6.5) for the reconstructed meta-fermentation was favorable for the respective pure cultures of the three selected strains. The l-lactic acid production performance of the reconstructed meta-fermentation system was as follows: concentration, 24.5g L-1 ; optical purity, 100%; productivity, 0.341g L-1 h-1 ; yield, 1.06g g-1 . These results indicated that constant pH control was effective in the reconstructed meta-fermentation with the best performance of l-lactic acid production at pH optimal for the selected bacterial growth, while the switching from swing pH control would suppress the activities of unfavorable bacterial species in un-isolated meta-fermentation.

Third-generation L-Lactic acid production by the microwave-assisted hydrolysis of red macroalgae Eucheuma denticulatum extract

The development of an efficient third-generation L-lactic acid (L-LA) production process from Eucheuma denticulatum extract (EDE) was achieved in this study. Microwave-assisted dilute acid hydrolysis (MADAH) and microwave-assisted hydrothermal hydrolysis (MAHTH) were chosen as the hydrolysis of EDE for the objective of increasing galactose yield. Single-factor optimization of hydrolysis of the EDE was studied, MADAH had high performance in galactose production relative to MAHTH, in which the yield and optimal conditions for both processes were 50.7% (0.1 M H2SO4, 120 °C for 25 min) and 47.8% (0 M H2SO4,160 °C for 35 min), respectively. For fermentation, the optimal L-LA yield was achieved at the inoculum cell density of 4% (w/w) Bacillus coagulans ATCC 7050 with 89.4% and 6% (w/w) Lactobacillus acidophilus LA-14 with 87.6%. In addition, lipid-extracted Chlorella vulgaris residues (CVRs) as co-nutrient supplementation increased the relative abundance of B. coagulans ATCC 7050, thus benefiting L-LA production.