Simultaneous Lactic Acid Production Research Articles

Lactobacillus pentosus enabled bioleaching of red mud at high pulp density and simultaneous production of lactic acid without supplementation of neutralizers

Heterogenous bioleaching by microorganisms producing organic acids is deemed as a compelling pathway for the recovery of valuable metals from red mud, but it is often performed at low pulp density, making this process not economically competitive. Here, Lactobacillus pentosus was employed to bioleach red mud at high pulp density and simultaneously produce lactic acid. The bioleaching performance of L. pentosus was first compared with Aspergillus niger and Gluconobacter oxydans, two most commonly used bioleaching strains. At 20 wt% pulp density and with pure glucose as a carbon source, L. pentosus could leach 31 % Al from red mud, while the leaching efficiency did not exceed 1 % for other two strains. Increasing the pulp density to even 30 wt% did not compromise the leaching efficiency of L. pentosus. When the enzymatic hydrolysate of rice straw was used to replace pure glucose as a carbon source, a comparable leaching efficiency of 30 % for Al was achieved, demonstrating that rice straw could be a cheap and renewable feedstock for bioleaching. Moreover, the alkali contained in red mud eliminated the addition of costly neutralizer as did in traditional lactic acid fermentation, enabling the simultaneous production of approximately 80 g/L lactic acid. Overall, this study offered a potentially economical and effective pathway for the bioleaching of red mud at high pulp density, and opened a new avenue for the production of lactic acid from lignocellulosic biomass.

Merging biomass and CO2 utilization; process design and assessment on simultaneous production of lactic acid and formic acid from glycerol and CO2

Biomass and CO2 conversion is receiving great attention to address climate change and energy crisis. Bio-based lactic acid (LA) appeals industries, however, current technologies suffer from low productivity and waste production. The transfer hydrogenation of glycerol and CO2 to LA and formic acid (FA) has been proposed as an alternative pathway, but further development and process design are required. This study proposes the integrated process for conversion of glycerol and CO2 to LA and FA derivatives. A two-pot/two-step transfer hydrogenation was demonstrated to achieve high products yield, catalyst reusability, and product separation. The esterification of lactate and formate salts to corresponding esters utilizing CO2 was also developed, which reduces H2SO4 consumption and K2SO4 waste. Techno-economic and life cycle assessments reveal that CO2 utilization is crucial for high economic benefit and low climate change impact. This study shows integrating biomass and CO2 could have synergies to design greener process.

Single-atom zinc catalyst for co-production of hydrogen and fine chemicals in soluble biomass solution

Single-atom photocatalysts (SAPCs) have attracted great interests due to their remarkable atom utilization efficiency, excellent activity, and selectivity, yet no application in synchronous biorefinery and water splitting. Here, efficient SAPCs based on atomically dispersed Zn atoms on carbon nitride (named Zn−mCN) were produced. Experiments verified that Zn−mCN has widened adsorption range of visible-light and lowered ability of electron−hole recombination, leading to excellent photocatalytic redox activity for synchronous biorefinery and water splitting to co-produce lactic acid (selectivity up to 91.0%) and hydrogen (∼15898.8 ​μmol ​g − 1 ​h − 1 ). This system has excellent universality for small- molecule monosaccharides and macromolecular xylan. Poisoning experiments showed that h + , 1 O 2 , ·O 2 − and ·OH can promote the simultaneous production of lactic acid and hydrogen. This work realized full utilization of whole redox reaction and provided a novel strategy for efficient and concomitant production of hydrogen and value-added chemicals from biomass-derived feedstocks aqueous solutions. The Zn@mCN single atom photocatalyst with Zn-N6 coordination has widened adsorption range of visible light and lowered ability of electron-hole recombination, leading to excellent photocatalytic redox activity for synchronous biorefinery and water splitting to co-produce lactic acid and hydrogen. Meanwhile, this system presents excellent universality for small molecule monosaccharides and macromolecular xylan.

Lachancea fermentati Strains Isolated From Kombucha: Fundamental Insights, and Practical Application in Low Alcohol Beer Brewing.

With a growing interest in non-alcoholic and low alcohol beer (NABLAB), researchers are looking into non-conventional yeasts to harness their special metabolic traits for their production. One of the investigated species is Lachancea fermentati, which possesses the uncommon ability to produce significant amounts of lactic acid during alcoholic fermentation, resulting in the accumulation of lactic acid while exhibiting reduced ethanol production. In this study, four Lachancea fermentati strains isolated from individual kombucha cultures were investigated. Whole genome sequencing was performed, and the strains were characterized for important brewing characteristics (e.g., sugar utilization) and sensitivities toward stress factors. A screening in wort extract was performed to elucidate strain-dependent differences, followed by fermentation optimization to enhance lactic acid production. Finally, a low alcohol beer was produced at 60 L pilot-scale. The genomes of the kombucha isolates were diverse and could be separated into two phylogenetic groups, which were related to their geographical origin. Compared to a Saccharomyces cerevisiae brewers’ yeast, the strains’ sensitivities to alcohol and acidic conditions were low, while their sensitivities toward osmotic stress were higher. In the screening, lactic acid production showed significant, strain-dependent differences. Fermentation optimization by means of response surface methodology (RSM) revealed an increased lactic acid production at a low pitching rate, high fermentation temperature, and high extract content. It was shown that a high initial glucose concentration led to the highest lactic acid production (max. 18.0 mM). The data indicated that simultaneous lactic acid production and ethanol production occurred as long as glucose was present. When glucose was depleted and/or lactic acid concentrations were high, the production shifted toward the ethanol pathway as the sole pathway. A low alcohol beer (<1.3% ABV) was produced at 60 L pilot-scale by means of stopped fermentation. The beer exhibited a balanced ratio of sweetness from residual sugars and acidity from the lactic acid produced (13.6 mM). However, due to the stopped fermentation, high levels of diacetyl were present, which could necessitate further process intervention to reduce concentrations to acceptable levels.

Bioprocessing of agro-industrial residues into lactic acid and probiotic enriched livestock feed.

Growing challenges of resource depletion, food security and environmental protection are putting stress on the development of biorefinery processes for bioprocessing of residues from food and agro-industry into value-added products. In this study, the simultaneous production of lactic acid (LA) and livestock feed on a combined substrate based on molasses and potato stillage by Lactobacillus paracasei NRRL B-4564 immobilized onto sunflower seed hull (SSH), brewer's spent grain (BSG) and sugar beet pulp (SBP) was studied. The highest total LA concentration of 399 g L-1 with overall productivity of 1.27 g L-1 h-1 was achieved in repeated batch fermentation by SBP-immobilized biocatalyst, followed by BSG- and SSH-immobilized cells. Fermentation improved the content of proteins and ash, and decreased the content of fibers in all three support materials. In addition, the fermentation had favorable effect on in vitro dry matter digestibility and energy values of SSH and BSG. According to assessment of probiotic potential, L. paracasei demonstrated a favorable probiotic profile, exhibiting high resistance to simulated ruminant digestive tract and significant antioxidant and antimicrobial activity. The proposed strategy enables valorization of agro-industrial residues as value-added ruminant feed and simultaneous LA production. Following principles of circular economy, the developed process combines different raw materials and integrates them into a biorefinery process, improving the overall profitability and productivity. © 2019 Society of Chemical Industry.

Simultaneous Bioconversion of Gelatinized Starchy Waste from the Rice Noodle Manufacturing Process to Lactic Acid and Maltose-Forming α-Amylase by Lactobacillus plantarum S21, Using a Low-Cost Medium

A direct bioconversion of gelatinized starchy waste (GSW) to lactic acid by amylolytic lactic acid bacterium Lactobacillus plantarum S21 was investigated. Corn steep liquor (CSL) was selected as the most suitable low-cost nitrogen source for replacing yeast extract, beef extract, and peptone in De Man, Rogosa and Sharpe (MRS) medium. Plackett–Burman design results indicated that GSW and CSL were the two most nutrients that significantly influence lactic acid production, among eight medium components, including GSW, CSL, K2HPO4, CH3COONa, (NH4)2HC6H5O7, MgSO4, MnSO4, and Tween 80. A new low-cost medium containing only GSW (134.4 g/L) and CSL (187.7 g/L) was achieved as omitting other six components from the optimized medium had no effect on lactic acid yield. Batch fermentation at 37 °C both in 1 L and 10 L jar fermenters showed non-significantly different productivity. A by-product, maltose-forming α-amylase, was successfully achieved up to 96% recovery yield using an ultrafiltration unit equipped with a 50 kDa cut-off membrane. Crude lactic acid exhibited the additional benefit of antimicrobial activity against food and feed pathogens Salmonella enterica serovar Typhimurium TISTR 292, Vibrio cholerae TH-001, and also E. coli ATCC 25922. This study presents a promising bioprocess for the simultaneous production of lactic acid, and a value-added food enzyme, using only two industrial wastes, GSW and CSL, as the medium components.

PH stabilization of lactic acid fermentation via the glutamate decarboxylation reaction: Simultaneous production of lactic acid and γ-aminobutyric acid

Neutralization of H+ enhances the substrate conversion rate and affords high product concentrations during lactic acid fermentation. Glutamate decarboxylase (GAD) consumes H+ and catalyzes the α-decarboxylation of glutamate to generate neutral γ-aminobutyric acid (GABA). In this study, the glutamate decarboxylation reaction, mediated by immobilized GAD, was applied to consume the H+ ions produced during lactic acid fermentation by Rhizopus oryzae As3.819. The glutamate decarboxylation reaction could neutralize the H+ produced during fermentation, thereby stabilizing the pH during lactic acid production, while lactic acid fermentation provided H+ for GABA production. By coupling the two biochemical processes (pH 4.7–5.0), a lactic acid concentration of 80.2g/L with a yield of 67% from glucose and a GABA concentration of 44.8g/L with 96.7% conversion from glutamate were obtained. These results indicated that the two biochemical processes could be coupled in a single reactor, thereby enabling the production of lactic acid and GABA simultaneously and economically.

Simultaneous production of lactic acid and propylene glycol from glycerol using solid catalysts without external hydrogen

Development of value-added chemicals from glycerol, the co-product with biodiesel, is imperative in sustaining the biodiesel industry. Combined usage of a solid base and a copper-based catalyst provided a catalytic pathway to convert glycerol to racemic lactic acid. A new pathway was found that during the glycerol-to-lactic acid conversion, hydrogen was formed, which could be used in situ to generate propylene glycol catalyzed by the copper-based catalyst. This new pathway was attested by results of systematically experimental study investigating the synergistic functions of a base catalyst (CaO, MgO, or SrO) and a copper-based dehydrogenation catalyst (Cu, CuO, Cu2O, or Cu2Cr2O5). Different combinations of catalysts and reaction conditions provided a tunable range for the yield of lactic acid and propylene glycol. Emphasis was put on the combined use of CuO and CaO due to their inexpensive availability and ease of recyclability; at optimal reaction conditions, the yield of lactic acid reached 52mol% together with 31mol% yield of propylene glycol.

A bioprocess for the remediation of anaerobically digested molasses spentwash from biogas plant and simultaneous production of lactic acid

A bacterial isolate LAB-1 identified as Lactobacillus casei was cultivated in a fermentation medium containing biogas plant effluent. This effluent was generated after anaerobic digestion of molasses spentwash in biogas fermenters. In the bioremediation process of this very dark coloured effluent through the cultivation of L. casei, decrease in effluent's colour of 49 and 52% and reduction in COD level up to 54 and 57% were achieved using bacterial cells in free and immobilised system, respectively, in 5 days batch cultivation. During this process of bioremediation, a metabolite lactic acid was produced by this bacterial isolate with the yield of 10.9 and 11.3 mg/ml, in free and immobilised cells fermentation, respectively.

Integrated bioprocess for the simultaneous production of lactic acid and dairy sewage treatment

An integrated biological process was developed for the conversion of whey lactose to lactic acid. We report about the achievement of maximum COD reduction and thus a substantial unburdening of the environment, combined with the economic production of lactic acid, appropriate for industrial scale. The process – designed for continuous operation – consists of four main steps: (i) Protein recovery by ultrafiltration leading to the first product: protein concentrate. The resulting filtrate is the fermentation substrate acid whey permeate. (ii) Adjustment of the composition of the permeate in the medium preparation step in order to ensure the proper function of the following process steps. (iii) Conversion of the lactose to lactate by fermentation with lactic acid bacteria in a cell recycle reactor, using ceramic microfiltration membranes. (iiii) Conversion of the lactate in the cell-free permeate stream of the fermentation to free lactic acid by bipolar electrodialysis.