Continuous production of lactic acid from deproteinized whey by coimmobilizedlactobacillus caseiandlactococcus lactiscells in a packed‐bed reactor

Photocatalytic conversion of biomass is considered an effective, clean, and environmentally friendly route to obtain high-valued chemicals and hydrogen. However, the limited conversion efficiency and poor selectivity are still the main bottlenecks for photocatalytic biomass conversion. Herein, we report the highly selective photocatalytic conversion of glucose solution on holo-symmetrically spherical three-dimensionally ordered macroporous TiO₂-CdSe heterojunction photonic crystal structure (s-TCS). The obtained s-TCS photocatalysts show excellent stability and strong light harvesting, uniform mass diffusion and exchange, and efficient photogenerated electrons/holes separation and utilization. The optimized s-TCS-4 photocatalyst displays the highest photocatalytic performance for glucose oxidation and hydrogen production. The glucose conversion, lactic acid selectivity, and yield on s-TCS-4 are about 95.9%, 94.3%, and 96.4%, respectively. The photocatalytic production of lactic acid for s-TCS-4 (18.5 g/L) is 2.3 times higher than the pure spherical TiO₂ photonic crystal without CdSe (s-TiO₂, 8.1 g/L), and the hydrogen production rate of s-TCS-4 is 9.4 times that of s-TiO₂. For the first time, we reveal that the photocatalytic conversion of glucose to lactic acid is a third-order and four-electron-involved reaction. This work could shed some new light on the efficient photocatalysis conversion of biomass to highly value-added products with high selectivity and yield, and simultaneously sustainable hydrogen evolution.

Lactic Acid as a platform chemical has broad application in various industries, especially in the production of Poly Lactic Acid (PLA) for biodegradable plastic. Empty fruit bunch (EFB), abundant by product from palm oil mill industry, is one of potential feedstock to be used in the production of lactic acid from lignocellulose biomass. EFB contains high cellulose and hemicellulose about 37– 59.7% w/w and 16–28% w/w, respectively. The aim of this paper is to study the effects of the operating conditions, such as temperature, reaction time, biomass loading, and catalyst concentration on the yield of lactic acid using barium hydroxide as alkaline catalyst. EFB pretreatment with steam explosion was applied to remove lignin content. The results showed that pretreatment reduced the lignin content from 22.66% to 9.69% w/w. Meanwhile, hemicellulose and cellulose increased from 14.40% to 16.40% w/w and 29.37% to 63.57% w/w, respectively. The highest yield of lactic acid was 21.57% C-mol, achieved by using 0.25 M Ba(OH)2 as the catalyst, with 5% w/v biomass loading, temperature 240°C, during 4 h reaction times. The yield was approximately equal to yield of lactic acid (~ 20%) compared with Pb2+ as the catalyst for EFB conversion although the later catalyst produced fewer by products during conversion.

Lactic acid fermentations were conducted using water hyacinth. It is known that the pretreatment and enzyme hydrolysis process optimize the potential of water hyacinth. Lactic acid produced by using lactic acid bacteria. All cells were grown at <TEX>$37^{\circ}C$</TEX> and initial pH 5.5. Lactic acid production was measured by HPLC. All Lactobacillus strains could produce lactic acid from pretreated water hyacinth. The highest lactic acid was achieved when lactic acid fermentation was carried out by L. delbrueckii for D-form and L. helveticus for L-form lactic acid production. The lactic acid concentration was 10.70 g/L by L. delbrueckii and it converted glucose in the medium to lactic acid, almost perfectly. Lactic acid production became higher when fermentation was carried out at a controlled pH 5.5. Lactic acid yield and productivity were 0.52 g/g and 0.19 g/L/h for L. helveticus, while L. delbrueckii was 0.64 g/g and 0.27 g/L/h. This study showed that water hyacinth medium could be alternative medium which can replace the complex and expensive medium for growing Lactobacillus strains in production of lactic acid.

Production of lactic acid from paper sludge using acid-tolerant, thermophilic Bacillus coagulan strains

Lactic acid fermentation from food waste with indigenous microbiota: Effects of pH, temperature and high OLR

In the current work, date wastes were used for lactic acid (LA) production under thermo-alkaline conditions to overcome some fermentation challenges. Amongst 27 bacterial isolates that produced LA from date juice, isolate D-218 exhibited better growth stability and LA production under various stressed conditions. This isolate was characterized as Bacillus coagulans D-218 using physiological and molecular identification methods. In batch fermentation mode, strain D-218 could not completely utilize 80 g/L of the total sugar and produced only 45.8 ± 2.8 g/L of LA at LA productivity of 0.214 g/L.h and high residual sugar (29.2 g/L) was unutilized in the fermentation media. Different repeated batch fermentations with different initial sugar concentrations and gradual increase in sugar concentrtions were conducted to maximize LA productivity. Starting with 60 g/L of total sugar, four runs of repeated batch fermentations were conducted that enhanced the LA productivity (70%) to 0.49 g/L.h. Another 9 runs were initiated with 40 g/L which further improved LA productivity that reached up to 0.77 g/L.h. Surprisingly, initiating fermentations with 20 g/L of total sugar successfully attained long-term fermentation (18 runs) with high LA yield and productivity without carbon loss of initiated startup sugar of date waste. In this process, strain D-218 could completely consume 80 g/L sugars with high LA production titer (72.9 ± 0.56 g/L), yield (0.92 g/g), and productivity (0.71 g/L.h). This study is the first to exploit date waste in a cost-effective system for high-titer lactic acid production under thermo-alkaline conditions (pH 9.0; 50 °C) and to report repeated batch fermentation for LA production from date wastes.

A rotating fibrous-bed bioreactor (RFB) was developed for fermentation to produce L(+)-lactic acid from glucose and cornstarch by Rhizopus oryzae. Fungal mycelia were immobilized on cotton cloth in the RFB for a prolonged period to study the fermentation kinetics and process stability. The pH and dissolved oxygen concentration (DO) were found to have significant effects on lactic acid productivity and yield, with pH 6 and 90% DO being the optimal conditions. A high lactic acid yield of 90% (w/w) and productivity of 2.5 g/L.h (467 g/h.m(2)) was obtained from glucose in fed-batch fermentation. When cornstarch was used as the substrate, the lactic acid yield was close to 100% (w/w) and the productivity was 1.65 g/L.h (300 g/h.m(2)). The highest concentration of lactic acid achieved in these fed-batch fermentations was 127 g/L. The immobilized-cells fermentation in the RFB gave a virtually cell-free fermentation broth and provided many advantages over conventional fermentation processes, especially those with freely suspended fungal cells. Without immobilization with the cotton cloth, mycelia grew everywhere in the fermentor and caused serious problems in reactor control and operation and consequently the fermentation was poor in lactic acid production. Oxygen transfer in the RFB was also studied and the volumetric oxygen transfer coefficients under various aeration and agitation conditions were determined and then used to estimate the oxygen transfer rate and uptake rate during the fermentation. The results showed that the oxygen uptake rate increased with increasing DO, indicating that oxygen transfer was limited by the diffusion inside the mycelial layer.

Direct production of l (+) lactic acid in a continuous and fully membrane-integrated hybrid reactor system under non-neutralizing conditions

Continuous mix batch bioreactors were used to study the kinetic parameters of lactic acid fermentation in microaerated-nutrient supplemented, lactose concentrated cheese whey using Lactobacillus helveticus. Four initial lactose concentrations ranging from 50 to 150 g l−1 were first used with no microaeration and no yeast extract added to establish the substrate concentration above which inhibition will occur and then the effects of microaeration and yeast extract on the process kinetic parameters were investigated. The experiments were conducted under controlled pH (5.5) and temperature (42 °C) conditions. The results indicated that higher concentrations of lactose had an inhibitory effect as they increased the lag period and the fermentation time; and decreased the specific growth rate, the maximum cell number, the lactose utilization rate, and the lactic acid production rate. The maximum lactic acid conversion efficiency (75.8%) was achieved with the 75 g l−1 initial lactose concentration. The optimum lactose concentration for lactic acid production was 75 g l−1 although Lactobacillus helveticus appeared to tolerate up to 100 g l−1 lactose concentration. Since the lactic acid productivity is of a minor importance compared to lactic acid concentration when considering the economic feasibility of lactic acid production from cheese whey using Lactobacillus helveticus, a lactose concentration of up to 100 g l−1 is recommended. Using yeast extract and/or microaeration increased the cell number, specific growth rate, cell yield, lactose consumption, lactic acid utilization rate, lactic acid concentration and lactic acid yield; and reduced the lag period, fermentation time and residual lactose. Combined yeast extract and microaeration produced better results than each one alone. From the results it appears that the energy uncoupling of anabolism and catabolism is the major bottleneck of the process. Besides lactic acid production, lactose may also be hydrolysed into glucose and galactose. The β-galactosidase activity in the medium is caused by cell lysis during the exponential growth phase. The metabolic activities of Lactobacillus helveticus in the presence of these three sugars need further investigation.

BackgroundEfficient conversion of lignocellulosic biomass to optically pure lactic acid is a key challenge for the economical production of biodegradable poly-lactic acid. A recently isolated strain, Thermoanaerobacterium aotearoense SCUT27, is promising as an efficient lactic acid production bacterium from biomass due to its broad substrate specificity. Additionally, its strictly anaerobic and thermophilic characteristics suppress contamination from other microoragnisms. Herein, we report the significant improvements of concentration and yield in lactic acid production from various lignocellulosic derived sugars, achieved by the carbon flux redirection through homologous recombination in T. aotearoense SCUT27.ResultsT. aotearoense SCUT27 was engineered to block the acetic acid formation pathway to improve the lactic acid production. The genetic manipulation resulted in 1.8 and 2.1 fold increase of the lactic acid yield using 10 g/L of glucose or 10 g/L of xylose as substrate, respectively. The maximum l-lactic acid yield of 0.93 g/g glucose with an optical purity of 99.3% was obtained by the engineered strain, designated as LA1002, from 50 g/L of substrate, which is very close to the theoretical value (1.0 g/g of glucose). In particular, LA1002 produced lactic acid at an unprecedented concentration up to 3.20 g/L using 10 g/L xylan as the single substrate without any pretreatment after 48 h fermentation. The non-sterilized fermentative production of l-lactic acid was also carried out, achieving values of 44.89 g/L and 0.89 g/g mixed sugar for lactic acid concentration and yield, respectively.ConclusionsBlocking acetic acid formation pathway in T. aotearoense SCUT27 increased l-lactic acid production and yield dramatically. To our best knowledge, this is the best performance of fermentation on lactic acid production using xylan as the sole carbon source, considering the final concentration, yield and fermentation time. In addition, it should be mentioned that the performance of non-sterilized simultaneous fermentation from glucose and xylose was very close to that of normal sterilized cultivation. All these results used the mutant strain, LA1002, indicated that it is a new promising candidate for the effective production of optically pure l-lactic acid from lignocellulosic biomass.

The present study investigated the synergistic effect of nutritional supplements (amino acid and Tween 80) on lactic acid production by Lactobacillus delbruckii utilizing a sugar refinery by product (cane molasses) in a submerged fermentation process. Initially, the effect of individual factors on lactic acid yield was studied by supplementing amino acids and their combinations, Tween 80 and cane molasses at varying concentrations in production medium. A combination of l-phenylalanine and l-lysine gave a maximum lactic acid yield of 47.89 ± 0.1 g/L on a dry cell weight basis at individual factor level. Similarly, maximum lactic acid yield was obtained by supplementing the production medium with 40.0 g/L and 2.0 g/L Tween 80 and cane molasses, respectively, at individual factor level. In order to further improve the lactic acid yield, nutritional supplements were optimized by central composite rotatable design (CCRD) using Minitab 15 software. Shake flask cultivation under optimized conditions, i.e., cane molasses (32.40 g/L), Tween 80 (2.0 g/L) and l-phenylalanine and l-lysine (34.0 mg/L) gave a lactic acid yield of 64.86 ± 0.2 g/L, corresponding to 95.0 % of the predicted yield of 67.78 ± 0.3 g/L. Batch cultivation performed in 7.5 L bioreactor (working volume: 3.0 L) under optimized conditions gave maximum lactic acid yield and productivity of 79.12 ± 0.2 g/L and 3.40 g/L·h, which is higher than previous studies with reduced fermentation time. Screening of lactic acid producing bacteria and characterization of lactic acid was also done.

Utilisation of microwave-NaOH pretreatment technology to improve performance and l-lactic acid yield from vinasse

Continuous fermentation of clarified corn stover hydrolysate for the production of lactic acid at high yield and productivity

Ethanol and lactic acid production as affected by sorghum genotype and location

The increasing demand for bio-based chemicals and sustainable materials has placed biomass-derived lactic acid in the spotlight as a key building block for biodegradable polylactic acid (PLA). Perennial ryegrass (Lolium perenne) is a promising feedstock due to its high dry matter (DM) yield, adaptability, and widespread agricultural use. This study investigates an integrated lactic acid–silage cascade process, focusing on how pH regulation, harvest timing, and biomass characteristics influence lactic acid production while maintaining agronomic efficiency. The results highlighted the crucial role of pH management and silage duration in optimizing lactic acid production. A silage period of 21 days was found to be optimal, as peak lactic acid yields were consistently observed at this stage. Maintaining a pH range of 4.5 to 6 proved essential for stabilizing fermentation, with citrate buffering at pH 6 leading to the highest lactic acid yields and minimizing undesirable by-products. Harvest timing also significantly affected lactic acid yield per hectare. While later harvesting increased total DM yield, it led to a decline in lactic acid concentration per kg DM. Tetraploid ryegrass (Explosion) maintained stable lactic acid yields due to higher biomass accumulation, whereas diploid varieties (Honroso) experienced a net reduction. From an agronomic perspective, optimizing harvest timing and variety selection is key to balancing biomass yield and fermentation efficiency. While tetraploid varieties offer greater flexibility, diploid varieties require precise harvest timing to avoid losses. These findings contribute to sustainable forage management, improving lactic acid production, silage efficiency, and agricultural resource use.