Highest Lactic Acid Yield Research Articles

Efficient synthesis of lactic acid from cellulose through the synergistic effect of zinc chloride hydrate and metal salts

The chemocatalystic conversion of cellulose, the main component of lignocellulosic biomass, to building-block chemicals in water under mild conditions, is an ideal but highly challenging process due to the robust crystal structure of cellulose. It is also the key to establishing a sustainable biomass-based chemical process. Here, we present a highly efficient and selective chemocatalytic hydrolysis of cellulose using ZnCl2·3H2O hydrate as the pretreatment reagent and water-compatible metal salts - ErCl3 as the catalyst, into lactic acid (LA), which is an important chemical building-block widely utilized in the food industry and in the production of chemicals and biodegradable plastic. With 94.0 % conversion of cellulose, an impressive LA yield of 84.6 % was achieved at 170 °C after 4 h under ambient air pressure in water. High yields of LA were also obtained from other carbohydrates, such as fructose (68.3 %), glucose (52.7 %), starch (54.4 %), and inulin (67 %). A series of experiments demonstrated that Er(III) combination with water catalyzed cascading steps of soluble cellulose into LA after ZnCl2·3H2O hydrate disrupted the hydrogen bonds in the cellulose, Zn(II) played an indirect role by promoting LA formation through inhibition of side reactions. A plausible mechanism was proposed for the chemocatalytic conversion of cellulose to LA.

An innovative temperature control strategy to improve optically pure L-lactic acid production from food waste

Fermentation of food waste to lactic acid (LA) is a strategy for resource recovery. However, the poor yield and optical activity (OA) of L-lactic acid (L-LA) are major bottlenecks for such efforts. This study focuses on enhancing L-LA yield and optical purity from the food waste without sterilization and inoculation at pilot-scale. First, the effects of temperature on LA production were explored. A higher LA yield but lower purity was obtained under mesophilic conditions, whereas the opposite results were represented at high temperature. On the basis of these findings, a novel two-stage temperature regulation strategy was developed that combined the benefits of both temperature conditions. This strategy not only ensured a L-LA yield of 0.371 g/g volatile solid, but also achieved a high optical purity of 98.0%. The underlying mechanism is that high temperature could enrich L-lactic acid bacteria (LAB) and inhibit LAB producing both L- and D-LA. Overall, this innovative strategy may be well-suited for generating optically pure L-LA from food waste fermentation.

A thermophilic L-lactic acid producer of high optical purity: isolation and identification

Biodegradable polymers, specifically polylactide, are an important part of food packaging and medical devices. Microbiological synthesis uses cheap renewable raw materials and industrial waste to produce a high yield of lactic acid, the monomer of polylactide. This method needs new effective lactic acid producing strains, e.g., thermophilic bacteria.
 The research involved thermophilic bacterial strains isolated from soil and compost samples. Their ability to produce organic acids and extracellular enzymes was tested using the method of high-performance liquid chromatography (HPLC) and microbiological tests respectively. The real-time polymerase chain reaction method (PCR) detected L-lactate dehydrogenase structural genes of L-lactate dehydrogenase of Bacillaceae. Strain T7.1 was fermented using glucose and yeast extract as carbon and nitrogen sources, respectively. The optical purity of lactic acid was evaluated using quantitative gas chromatography on a chiral column to separate lactate isomers. The molecular genetic analysis of the 16S rRNA gene sequence was applied to identify strain T7.1.
 The chromatographic analysis proved that 10 out of 13 isolated thermophilic strains were effective lactic acid producers. They demonstrated proteolytic, amylolytic, or cellulase activities. During the fermentation, strain T7.1 produced 81 g/L of lactic acid with a peak productivity at 1.58 g/(L·h). The optical purity of the product exceeded 99.9% L-lactate. The genetic analysis identified strain T7.1 as Weizmannia coagulans (Bacillus coagulans).
 The research revealed a promising thermophilic producer of optically pure L-lactic acid. Further research is needed to optimize the cultivation conditions, design an effective and cheap nutrient medium, and develop engineering and technological solutions to increase the yield.

Oxidative depolymerization of lignin to vanillin and lactic acid in an aqueous solution

A heterogeneous molybdenum (Mo)-based oxide catalyst system in combination with hydrogen peroxide as an oxidant was developed for oxidative depolymerization of lignin to yield high-value platform chemicals in a nearly neutral aqueous solution. The impact of various reaction conditions, including the ratios of H2O2 and/or MoO3/Al2O3 catalyst to lignin, reaction temperature and duration, and lignin concentration, were investigated in a batch system or a continuous flow fixed-bed system. The structural changes between dealkaline lignin and the recovered lignin (O-lignin and M−lignin) were analyzed using UV–vis, FT-IR, and GPC techniques. The combination of MoO3 and H2O2 resulted in a superior peroxo complex, promoting the formation of vanillin and lactic acid. The medium and weak acid feature of MoO3/Al2O3 catalyst induced the highest vanillin yield (5.6%) and the selectivity (86.9%) of main platform products. However, the highest yield of lactic acid (3.4%) was observed on MoO3/SiO2 with more weak acid sites. Hypothetical formation mechanisms for vanillin and lactic acid were proposed based on the depolymerization of lignin model compounds.

Effects of native Lachancea thermotolerans combined with Saccharomyces cerevisiae on wine volatile and phenolic profiles in pilot and industrial scale

Wines in the northwest region of China often suffer from poor color stability, low wine acidity, and inelegant aroma description. The Lachancea thermotolerans yeasts with a high yield of lactic acid and pleasant aroma compounds can ameliorate such wines. In this study, the performances of native L. thermotolerans CVE-LT1 co-inoculated with Saccharomyces cerevisiae in different ratios and strategies (simultaneous and sequential mode) were evaluated in pilot scale fermenter (60 L) and industrial scale fermenter (520 hL) of Cabernet Sauvignon grape must with high sugar/low acidity. Results evidenced that the mixed culture of L. thermotolerans and S. cerevisiae can significantly increase lactic acid level (up to 6.98 g/L) and decrease wine pH (up to 3.57). Meanwhile, the color parameters of a* and C* in mixed culture wines were improved. The higher concentrations of volatile compounds were mainly observed in sequential inoculation treatments, including the enhancement of ethyl lactate and 2-phenylethanol. As for phenolic compounds, L. thermotolerans promoted the formation of anthocyanins derivatives and phenolic acids in pilot and industrial fermentation. In conclusion, these results indicated that L. thermotolerans LT1 can be used in hot winery regions to improve the acidity, color indexes, phenolic compounds, and aroma quality of wines.

Catalytic Conversion of Sugars into Lactic Acid via a RuOx/MoS2 Catalyst

The catalytic transformation of sugars into lactic acid has shown great potential for the scalable utilization of renewable biomass. Herein, RuOx/MoS2 catalysts were synthesized with the assistance of CaO for the one-pot conversion of glucose to lactic acid. Under the reaction conditions of 120 °C and 1 MPa O2, a 96.6% glucose conversion and a 54.3% lactic acid selectivity were realized in the one-pot catalytic reaction, with relatively high stability after four successive cycles. This catalytic system was also effective for the conversion of many other carbohydrate substrates, such as fructose, xylose and cellulose (selectivity 68.9%, 78.2% and 50.6%, respectively). According to catalyst characterizations and conditional experiments, the highly dispersed RuOx species on the surface of MoS2, together with OH−, promoted isomerization, retro-aldol condensation, dehydration and hydration reactions, resulting in a relatively high lactic acid yield for sugar conversions.

Exploration of optimal reaction conditions on lactic acid production from glucose photoreforming over carbon nitride

Biomass valorization by photoreforming approach provides a promising and alternative strategy to generate value-added chemicals and fuels. In this work, we demonstrate the selective production of lactic acid from glucose photoreforming over pristine graphitic carbon nitride (g-C3N4) photocatalyst. Control experiments screen the best condition for the highest yield of lactic acid, including modulating pH, catalyst loading, and reaction time. 100% glucose conversion is achieved along with almost 100% lactic acid yield under the optimized condition. Density functional theory (DFT) calculations reveal that the rate-determining step (RDS) of the overall reaction on g-C3N4 is the conversion of pyruvaldehyde, where an electron transfer takes place. This present work provides experimental insights and theoretical understanding for selective lactic acid production from biomass photoreforming.

One Step Catalytic Conversion of Polysaccharides in Ulva prolifera to Lactic Acid and Value-Added Chemicals

The production of lactic acid and value-added chemicals (such as hydroxypropanone, glycolic acid, and formic acid) directly from Ulva prolifera via one-step catalytic process was studied. The effect of different amounts of YCl3-derived catalysts on the hydrothermal conversion of carbohydrates in Ulva prolifera was explored, and the reaction conditions were optimized. In this catalytic system, rhamnose could be extracted from Ulva prolifera and converted in situ into lactic acid and hydroxypropanone at 160 °C, while all the glucose, xylose, and rhamnose were fractionated and completely converted to lactic acid at 220 °C or at a higher temperature, via several consecutive and/or parallel catalytic processes. The highest yield of lactic acid obtained was 31.4 wt% under the optimized conditions. The hydrothermal conversion of Ulva prolifera occurred rapidly (within 10 min) and showed promise to valorize Ulva prolifera.

Isolation of Lactococcus sp. X1 from Termite Gut, and Its Application in Lactic Acid Production

The production of lactic acid (LA) from lignocellulosic biomass is an important route for the exploitation of renewable resources; nevertheless, effective LA production from this feedstock is challenged by several limitations, such as pentose and oligosaccharide utilization. In this study, a new strain, Lactococcus sp. X1, which is capable of fermenting glucose, xylose, and several disaccharides to produce L-lactic acid, was isolated from the gut of a wood-feeding termite, Coptotermes formosanus. Compared to conventional lactic acid bacteria, Lactococcus sp. X1 requires less complex nitrogen sources, which might in turn reduce the cost of LA production. In addition, Lactococcus sp. X1 was able to completely ferment 50 g/L of glucose within 3 days, giving a high LA yield of 99.9%, and its LA yield from 50 g/L of pretreated corncob reached up to 0.34 g/g substrates in the presence of a commercial cellulase. Strain X1 was also capable of excreting two kinds of nutritional factors, namely biotin and vitamin C, indicating its crucial role in the nourishment of the termite. In conclusion, Lactococcus sp. X1 is a new lactic acid bacterium, which may hold promise for application in cost-effective LA production as well as in the field of food additives.

Production of lactic acid from pasta wastes using a biorefinery approach

A total of 398 kt of pasta waste (PW), generated during the production process of pasta, were produced in 2021. Due to its chemical composition and practically zero cost, PW has already been studied as a raw material for the production of lactic acid (LA) through fermentations. The main objective of this article was to improve the economic viability of the process by replacing commercial enzymes, necessary for starch hydrolysis in PW, with raw enzymes also produced from wastes. Enzyme synthesis was achieved through solid-state fermentation (SsF) of wheat bran by Aspergillus awamori or Aspergillus oryzae at various moisture contents. The maximum amylase activity (52 U/g dry solid) was achieved after 2 days of fermentation with A. awamori at 60% of moisture content. After that, the enzymes were used to hydrolyse PW, reaching 76 g/L of total sugars, 65 g/L of glucose and a yield of 0.72 gglu/gds with the enzymes produced by A. awamori. Subsequently, the hydrolysate was fermented into LA using Bacillus coagulans A559, yielding 52 g/L and 49 g/L with and without yeast extract, respectively. Remarkably, compared to the process with commercial enzymes, a higher LA yield was reached when enzymes produced by SsF were added (0.80 gLA/gglu). Furthermore, the productivities between the two processes were similar (around 3.9 g/L/h) which highlights that yeast extract is not necessary when using enzymes produced by SsF.

Effect of thermal and ultrasonic pretreatment on lactic acid fermentation of food waste.

Food waste (FW) generation has become one of the largest environmental concerns for human society. Thanks to its chemical features and its high biodegradability, FW can be used as starting platform to produce biocommodities. Lactic acid (LA) is one of those chemicals that is gaining the attention of industry and research for its important role in polylactic acids production. To exploit better the organic content of FW, several FW pretreatments have been proposed in the literature, though none of them were aimed at influencing LA fermentation. Thermal and ultrasonic pretreatment effects on solubilization rates and LA production yields have been investigated in this batch study. The highest solubilization rate was achieved with 30 minutes ultrasonic pretreated FW resulting in a 15% increment in soluble COD (sCOD). The highest LA yield was obtained after 90-minute thermal pretreatment at 80 and 100°C at a yield of 0.49 g LA•g COD-1. This study shows that ultrasonic pretreatment generally performed better than thermal pretreatment when considering the increase in sCOD but caused a reduction in LA concentrations and yields after fermentation with high production of ethanol. The opposite trend was recorded in the thermal pretreated incubations, in which LA was present for 50% of the sCOD with higher LA concentrations of 2.90 g COD•L-1.

Chemoenzymatic conversion of glycerol to lactic acid and glycolic acid

Catalytic valorization of raw glycerol derived from biodiesel into high-value chemicals has attracted great attention. Here, we report chemoenzymatic cascade reactions that convert glycerol to lactic acid and glycolic acid. In the enzymatic step, a coenzyme recycling system was developed to convert glycerol into 1,3-dihydroxyacetone (DHA) with a yield of 92.3% in potassium phosphate buffer (300 mM, pH 7.1) containing 100 mM glycerol, 2 mM NAD+, 242 U/mL glycerol dehydrogenase-GldA and NADH oxidase-SpNoxK184R at 30 °C. Subsequently, NaOH or NaClO2 catalyzes the formation of lactic acid and glycolic acid from DHA. The high yield of lactic acid (72.3%) and glycolic acid (78.2%) verify the benefit of the chemoenzymatic approaches.Graphical

Efficient Catalytic Conversion of Glucose into Lactic Acid over Y-β and Yb-β Zeolites.

In this work, a new type of modified β zeolites with rare earth elements (ree) was discovered for producing lactic acid from glucose and achieved a good catalytic effect. At first, the catalytic performances of ree-β zeolites, ree oxides, and single-transition-metal-β zeolites were compared, and the result showed that Y-β and Yb-β zeolites had the best catalytic activity under the same reaction conditions. Under the best reaction conditions, the maximum yields of lactic acid with Y-β and Yb-β catalysts were 45.3 and 43.6%, respectively. The acid characterization showed that Y/Yb-β zeolites had a similar number of Lewis acid sites as Sn-β zeolites, and they were also more than other transition-metal-β zeolites. Thus, Y-β and Yb-β zeolites had a higher lactic acid yield than those catalysts. It is interesting to note that Y-β and Yb-β zeolites owned more Brønsted acids but produced fewer byproducts. Combining the decomposition experiment of 5-hydroxymethyl furfural, fewer byproducts were produced with Y-β and Yb-β zeolites because the low amount of Brønsted acid contained could hinder the decomposition of 5-hydroxymethyl furfural, thereby slowing down the side reaction.

Direct lactic acid production from household food waste by lactic acid bacteria

China is vigorously promoting garbage classification, but the treatment of classified waste, especially household food waste (HFW) has yet to be studied. Lactic acid (LA), a high value-added platform molecule has broad market prospects. Although there have been many studies on the production of LA from food waste, open fermentation often produces lots of by-products, while the traditional fermentation under a pure bacteria system often requires the saccharification process, which increases the production cost. We sought to analyze the comprehensive properties of classified HFW in Shanghai, then to produce LA by inoculating lactic acid bacteria (LAB) directly. The effects of strains, temperature, sterilized or not, initial pH, inoculum size, and substrate concentration on LA production were investigated. HFW was rich in nutrients and growth factors which provided the possibility for direct LA production from HFW by inoculating LAB. The results showed that Lactobacillus rhamnosus ATCC 7469, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus all could be used as the inoculum, however, no significant synergistic effect of the three strains on LA production was found. LA concentration of 30.25 g/L at 37 °C, pH 6.8 could be obtained by inoculating Lactobacillus rhamnosus ATCC 7469 from sterilized HFW. High inoculum size and substrate concentration resulted in high LA concentration, but not high LA yield. The result of ANOVA indicated that there was a significantly positive relationship between substrate concentration and LA concentration (r = 0.942, p < 0.01), while no statistically significant difference between these groups at different inoculum size was evident (p = 0.318). In addition, an average LA concentration of 26.8 g/L, LA yield of 0.20 g/g TCOD was obtained by repeated batch fermentation for 32 d.

Microwave-induced controlled-isomerization during glucose conversion into lactic acid over a Sn-beta catalyst

Altered fructose tautomeric equilibria and following reverse-isomerization from fructose to glucose enabled a high lactic acid yield of 68.3 wt% over the “monolithic” Sn-beta catalyst, which is attributed to the non-thermal effect of microwave.

Lactic acid production from mesophilic and thermophilic fermentation of food waste at different pH

It is promising to recover lactic acid (LA) from fermentation of food waste (FW). In this study, pH and temperatures were investigated comprehensively to find their effects on LA fermentation, and microbial analyses were used to take insight to the variation of LA production. The results showed that mesophilic fermentation benefited hydrolysis and acidification, leading to a high yield of LA, while thermophilic conditions restricted other producers at low pH, leading to a high purity of LA. Lactobacillus amylolyticus was the main LA producer under thermophilic conditions, but Thermoanaerobacterium thermosaccharolyticum boomed at pH 5.0–6.0 and it converted LA partly to butyric acid. Simultaneously, Bacillus coagulans also increased and improved the optical purity (OP) of L-LA. From a series of this study, an operational condition of pH 5.5 and temperature of 52 °C would be potentially suitable for lactate fermentation of FW with high purity of 89%, while a stable LA production with an OP of 68% was achieved at 55 °C and pH 6.0.

In vivo evolution of lactic acid hyper-tolerant Clostridium thermocellum

Lactic acid (LA) has several applications in the food, cosmetics and pharmaceutical industries, as well as in the production of biodegradable plastic polymers, namely polylactides. Industrial production of LA is essentially based on microbial fermentation. Recent reports have shown the potential of the cellulolytic bacterium Clostridium thermocellum for direct LA production from inexpensive lignocellulosic biomass. However, C. thermocellum is highly sensitive to acids and does not grow at pH < 6.0. Improvement of LA tolerance of this microorganism is pivotal for its application in cost-efficient production of LA. In the present study, the LA tolerance of C. thermocellum strains LL345 (wild-type fermentation profile) and LL1111 (high LA yield) was increased by adaptive laboratory evolution. At large inoculum size (10 %), the maximum tolerated LA concentration of strain LL1111 was more than doubled, from 15 g/L to 35 g/L, while subcultures evolved from LL345 showed 50–85 % faster growth in medium containing 45 g/L LA. Gene mutations (pyruvate phosphate dikinase, histidine protein kinase/phosphorylase) possibly affecting carbohydrate and/or phosphate metabolism have been detected in most LA-adapted populations. Although improvement of LA tolerance may sometimes also enable higher LA production in microorganisms, C. thermocellum LA-adapted cultures showed a yield of LA, and generally of other organic acids, similar to or lower than parental strains. Based on its improved LA tolerance and LA titer similar to its parent strain (LL1111), mixed adapted culture LL1630 showed the highest performing phenotype and could serve as a framework for improving LA production by further metabolic engineering.

Optimization of lactic acid production from agro-industrial wastes produced by Kosakonia cowanii

Lactic acid is used for the preparation of poly-lactic acid. The objective of this research was to produce lactic acid from agro-industrial wastes as cheap, renewable substrates, and also reduce the pollution burden on the environment. Sixteen bacterial isolates were isolated from agro-industrial wastes. The chemical hydrolysis of agro-industrial wastes was achieved with hydrochloric acid, sulfuric acid, and sodium hydroxide. The highest yield of lactic acid produced was identified using 16S rRNA. The optimum conditions for lactic acid production were determined. Calcium lactate, produced from the culture fermentation was treated with sulfuric acid to precipitate the calcium sulfate. The filtrate holding free organic acid was vaporized to produce pure lactic acid. Chemical hydrolysis using 5% HCl released the highest concentration of total reducing sugar at 8015.90 and 7761.55 ​mg/L using cotton and coffee wastes, respectively. The bacterial isolate Kosakonia cowanii (B2) presented highest lactic acid concentration at 24.97 and 27.91 ​g/L after 24 and 48 ​h, respectively as a qualitative determined by HPLC analysis. The maximum lactic acid production at 28.14 ​g/L was obtained on the fermenter scale after 72 ​h by HPLC analysis.

The fabrication of BaTiO3 supported AuPd nanoparticles for selective oxidation of 1,2‐propanediol to lactic acid

AbstractBACKGROUNDThe oxidation of 1,2‐propanediol under alkaline conditions in the presence of a heterogeneous catalyst can be tailored to the formation of lactic acid, an important commodity chemical. In the present study, BaTiO3 supported bimetallic AuPd nanoparticles was fabricated by sol‐immobilized method and investigated by different characterizations. The optimum operating parameters of 1,2‐propanediol catalytic oxidation were explored via the combination of single factor experiment and response surface methodology.RESULTSThe high lactic acid yield of 81.4% can be obtained under optimum operating conditions (106 °C, 1.1 MPa O2 pressure, and NaOH/1,2‐PDO molar ratio of 3.0). The results of single factor experiment indicated that selectivity to lactic acid decreased with prolonging the reaction time, but increasing the temperature, NaOH concentration and O2 pressure appeared to decrease the lactic acid selectivity after an initial increase. Reaction kinetics indicated that the value of Ea was 39.2 kJ·mol−1 over AuPd/BaTiO3 catalyst. After five runs, the AuPd/BaTiO3 catalyst stills retained high activity.CONCLUSIONThe AuPd/BaTiO3 catalyst exhibited a good catalytic activity for this selective oxidation while the coalescence of Au and Pd nanoparticles can enhance the selectivity to lactic acid. NaOH/1,2‐PDO molar ratio imposed an extremely comparable impact on lactic acid yield. The mutual interactions between reaction temperature and NaOH/1,2‐PDO molar ratio, as well as NaOH/1,2‐PDO molar ratio and pressure, were of vital significance. © 2021 Society of Chemical Industry (SCI).

Simulation of continuous catalytic conversion of glycerol into lactic acid in a microreactor system: A CFD study

Hand in hand with the flourish of the biodiesel industry, glycerol (GLY) as an inconvenient by-product has generated environmental and sustainability concerns. Devising measures for efficient transformation of GLY into value-added products is a promising solution. In this contribution, the transformation of GLY to lactic acid (LA) as a valuable chemical was investigated in a continuous process for industrial applications. In this regard, a catalytic method using heterogeneous Cu nanoparticles in NaOH solution was studied in a microreactor by a CFD simulation. A seven-inlet micromixer comprising an optimized mixing unit was incorporated for uniform distribution of the species. The effects of various parameters upon the process performance were considered and the optimum points were determined. Also, the extent of the influence of each variable on LA yield was evaluated using sensitivity analysis techniques. While higher LA yield could be obtained at extreme scenarios, optimum values of the Re and temperature for obtaining the maximum performance under sensible operating conditions were determined to be 0.108 and 510.1 K which led to the optimum yields of 67.8% and 59.5%, respectively. Moreover, the sensitivity analysis revealed that the molar ratio of OH−/GLY and temperature were the most and least significant parameters, respectively.