Bioconversion of waste cellulosic biomass into high-value chemicals holds significant potential, although traditional cocultures face challenges such as microbial competition and poor spatial organization, which limit stability and efficiency. Herein, we, for the first time, created enzyme-bacteria symbionts with customized geometric configurations using a three-dimensional (3D) bioprinting platform for efficient lactic acid production from cellulose. To facilitate 3D printing, a biocompatible and tunable dual-network functional living bioink was developed with optimized rheological properties, enabling meticulous manipulation of the spatial arrangement and density of active components. By optimizing spatial niches, the design featuring an inner cellulase layer and an outer bacteria layer improved lactic acid production efficiency during cellulose bioconversion. At an optimal enzyme loading of 35 U/mL, the maximum lactic acid yield of 6.55 ± 0.34 g/L was achieved using 3D-bioprinted symbionts with 17.5 g/L cellulose as the sole carbon source. Importantly, reaction-diffusion simulations clearly revealed the spatial and radial distributions of the intermediate product glucose and the final product lactic acid within the enzyme-bacteria symbionts. This work establishes a new design paradigm for engineered living materials, providing a scalable platform for diverse waste-to-product conversions and practical pathways for implementing circular bioeconomy principles.

The fruit waste of pineapple peel and jackfruit rag contains rich amount of carbohydrates can be tuned as substrates for the cultivation of bacteria and fungi. These wastes were also used as raw material for production of lactic acid. Increasing demand of lactic acid in food, bakery, pharmaceutical and cosmetic industries etc., had made it necessary to develop a sustainable and conventional method for lactic acid production by fermentation. The present study aimed for lactic acid production from pineapple peel and jackfruit rag. A total of 15 isolates were isolated from different fruit wastes by streak plate method and were identified as Lactic acid bacteria based on gram staining and biochemical tests. The physicochemical properties of pineapple peel and jackfruit rag were: pH (4.3 and 6.2), TSS in brix (12 and 19.5), moisture content (83.8% and 80%), respectively. Different pre-treatment methods were employed for the extraction of reducing sugars from pineapple peel and jackfruit rag. Among six pre-treatments, the substrate with 1 per cent hydrochloric acid followed by autoclave resulted the highest value of reducing sugars. The lactic acid production was carried out by inoculating the 5% lactic acid bacterial isolates (MM, G1 and A2) in acid hydrolysate of substrates and incubated at 30 ºC with 120 rpm for three days. Maximum Lactic acid yield was recorded with pineapple peel substrate (3.15%) than jackfruit rag (2.7%) after 3 days of incubation with MM isolate. This study highlights the potential of pineapple peel and jackfruit rag waste as a low cost and economically viable fermentation substrate for the production of lactic acid.

Macroalgae (Ulva fasciata, Gracilaria corticata, and Sargassum wightii) were collected from the marine environment and used as the substrate for lactic acid production. These macroalgae were pretreated with hydrochloric acid (0.2 to 0.4 N) for various times (20 to 60 min). Additionally, the algal hydrolysate was incubated with cellulase for 24 h at 30 ± 1 °C to achieve enzymatic saccharification. Proximate analysis of these macroalgae was performed, and the yield was high in G. corticata. The G. corticata hydrolysate was composed of 10.01 ± 0.12% ash content, 1.25 ± 0.2% total fat, 10.2 ± 0.1% crude protein, 9.2 ± 0.2% moisture content, and a higher level of total carbohydrate (69.33 ± 1.5%) than the other two macroalgae. In G. corticata, the enzymatic treatment showed the maximum reducing sugar (33.5 ± 2.3%) relative to the other macroalgal hydrolysates and was considered for optimization of lactic acid production. Lactobacillus acidophilus (MTCC447) utilized pretreated G. corticata hydrolysate (enriched with 5% yeast extract), and maximum lactic acid yield was achieved after 72 h, 30 °C incubation temperature, and 6% inoculum (1×108 CFU/mL) in static culture condition. Batch fermentation was performed in the 1-L bioreactor at room temperature (30 °C) for 96 h. Lactic acid production was maximum within 72 h and the pH value was depleted. The present finding indicates that G. corticata could be used as a substrate for lactic acid production.

Boron doping g-C3N4 supported Cu2O for photocatalytic reforming of xylose into lactic acid

Biomass upgrading – the conversion of biomass waste into value-added products – provides a possible solution to reduce global dependency on nonrenewable resources. This study investigates the possibility of green biomass upgrading for lactic acid production by electrochemically-driven degradation of glucose. Herein we report an electrooxidized copper(ii) electrode which exhibits a turnover frequency of 5.04 s−1 for glucose conversion. Chronoamperometry experiments under varied potentials, alkalinity, and electrode preparation achieved a maximum lactic acid yield of 23.3 ± 1.2% and selectivity of 31.1 ± 1.9% (1.46 V vs. RHE, 1.0 M NaOH) for a room temperature and open-to-atmosphere reaction. Comparison between reaction conditions revealed lactic acid yield depends on alkalinity and applied potential, while pre-oxidation of the copper had a negligible effect on yield. Post-reaction cyclic voltammetry studies indicated no loss in reactivity for copper(ii) electrodes after a 30 hour reaction. Finally, a mechanism dependent on solvated Cu2+ species is proposed as evidenced by similar product distributions in electrocatalytic and thermocatalytic systems.

‘Lactobacillus sp. strain TERI-D3’, as microbial cell factory for fermentative production of lactic acid’.

The development of sustainable methods with robust strains and renewable substrates for the production of high-value chemicals has gained much attention recently. This study investigates the effect of ten different microbial strains for lactic acid production from food waste through simultaneous saccharification and fermentation process at optimal conditions of pH 5.5–6.5 at 30 °C. The highest lactic acid concentration of 18.69 g L-1 was obtained from Lacobacillus manihotivorans DSM 13343, followed by 17.03 g L-1 from Lactobacillus plantarum DSM 20174 and 15.88 g L-1 from mixed culture during fermentation of food waste, whereas the strains produced only 12.72 g L-1, 17.75 g L-1, and 9.38 g L-1 respectively from MRS broth, therefore showing that the food waste was a superior substrate compared to the MRS broth for lactic acid fermentation. The maximum lactic acid yield was 0.73 g g-1, 0.71 g g-1, and 0.69 g g-1 with Lacobacillus manihotivorans DSM 13343, Lactococcus lactis subsp. lactis DSM 20481, and Lactobacillus plantarum DSM 20174 respectively with high selectivity for lactic acid up to 84%. Furthermore, this study has achieved significant lactic acid production with increased substrate utilization in lower processing time and reactor volume.

Parametric optimization is an effective way in fermentation process to improve product yield and productivity in order to save time, space and financial resources. In this study, Box–Behnken design was applied to optimize the conditions for lactic acid production by immobilized Lactobacillus pentosus ATCC 8041 cell fermentation. Two quadratic models and response surface methodology were performed to illustrate the effect of each parameters and their interactions on the lactic acid yield and glucose consumption rate in immobilized L. pentosus ATCC 8041 cell fermentation. The maximum lactic acid yield was obtained as 0.938 ± 0.003 g/g glucose with a productivity of 2.213 ± 0.008 g/(L × h) under the optimized conditions of 2.0 mm bead diameter, 5.60 pH, 115.3 g/L initial glucose concentration, and 398.2 mg biomass (CDW) in 100 mL hydrogel. The analysis of variance indicated that the quadratic model was significant and could be used to scale up the fermentation process.

Theutilization of sucrose, an easily accessible disaccharide,in the production of a versatile platform chemical lactic acid (LA),is more attractive than a monosaccharide. In this work, we reporta modification approach by 3-aminopropyltrimethoxysilane to introducean amino group onto the surface of the Sn-Beta Lewis acid catalyst.Using the modified catalyst, a maximum LA yield of 58% was achievedunder optimal hydrothermal conditions (190 °C, 4 h) from sucrose,along with a complete conversion and a reduced 5-hydroxymethylfurfural(HMF) yield of 8% compared to Sn-Beta. To evaluate the role of theamino group, different substrates were used as the reactants to produceLA. The experimental results suggested that both fructose and glucosewere crucial intermediates in the initial 2 h, whereas glucose isthe sole reactant after 2 h. Upon modification, not only the hydrolysisof sucrose was promoted, but the side reaction of HMF formation wasalso suppressed.

Graphene oxide (GO) was used as a catalyst support and for regeneration of a homogeneous catalyst in the catalytic conversion of glucose to lactic acid (LA). First, a solid base catalyst was prepared through the adsorption of Pb2+ ions by GO through ionic interaction with oxygenated groups of GO. The collected GO-Pb catalyst was characterized, demonstrating the successful loading of Pb2+ onto GO sheets using FTIR and XPS. The GO-Pb catalyst was subsequently used for the conversion of glucose into LA. A maximum LA yield of approximately 30% was achieved in 30 min. The catalyst demonstrated the ability to be used for at least five cycles. In contrast, the leached Pb2+ ions during the hydrothermal process were regenerated through adsorption with fresh GO. The regenerated catalyst demonstrated the possibility of the regenerated Pb2+ ions for further catalytic conversions of lactic acid. This study could be essential to produce valuable chemicals through the use of heterogeneous catalysts that are produced via a simple and environmental benign process.

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

This study investigated a fed-batch process for glycerol conversion to lactic acid with sodium hydroxide (NaOH) as homogeneous catalyst, with the aim to reduce the corrosiveness of catalyst to reactor. At the optimal conditions of the fed-batch process (1.1 M initial glycerol concentration, reaction time of 220 min, reaction temperature of 300 °C, NaOH concentration around 0.2 M), lactic acid yield reached 82 mol%, with 93 mol% of glycerol conversion. A first order kinetic model in the fed-batch conversion of glycerol was developed and validated under different process conditions. The corrosiveness to stainless steel reactor in glycerol conversion in the fed-batch process, measured as Fe3+ at the end of reaction, decreased from 9.5 to 1.5 ppm Fe3+ when compared to a batch process using a homogeneous 1.25 M NaOH as catalyst. Application of the fed-batch reactor in the crude glycerol conversion reached the maximum lactic acid yield of 72.9 mol% with 92.4 mol% glycerol conversion, but high soap content in crude glycerol has negative effects on both lactic acid yield and glycerol conversion.

Four types of straw, namely, soybean, wheat, corn, and rice, were investigated for use in lactic acid production. These straws were mainly composed of cellulose, hemicellulose, and lignin. After pretreatment with ammonia, the cellulose content increased, whereas the hemicellulose and lignin contents decreased. Analytical results also showed that the liquid enzymatic hydrolysates were primarily composed of glucose, xylose, and cellobiose. Preliminary experiments showed that a higher lactic acid concentration could be obtained from the wheat and soybean straw. However, soybean straw was chosen as the substrate for lactic acid production owing to its high protein content. The maximum lactic acid yield (0.8 g/g) and lactic acid productivity (0.61 g/(l/h)) were obtained with an initial reducing sugar concentration of 35 g/l at 30°C when using Lactobacillus casei (10% inoculum) for a 42 h fermentation period. Thus, the experimental results demonstrated the feasibility of using a soybean straw enzymatic hydrolysate as a substrate for lactic acid production.

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.

The natural mixed culture kefir was immobilized on boiled corn grains to produce an efficient biocatalyst for lactic acid fermentation with direct applications in food production, such as sourdough bread making. The immobilized biocatalyst was initially evaluated for its efficiency for lactic acid production by fermentation of cheese whey at various temperatures. The immobilized cells increased the fermentation rate and enhanced lactic acid production compared to free kefir cells. Maximum lactic acid yield (68.8 g/100 g) and lactic acid productivity (12.6 g/L per day) were obtained during fermentation by immobilized cells at 37 °C. The immobilized biocatalyst was then assessed as culture for sourdough bread making. The produced sourdough breads had satisfactory specific loaf volumes and good sensory characteristics. Specifically, bread made by addition of 60% w/w sourdough containing kefir immobilized on corn was more resistant regarding mould spoilage (appearance during the 11(th) day), probably due to higher lactic acid produced (2.86 g/Kg of bread) compared to the control samples. The sourdough breads made with the immobilized biocatalyst had aroma profiles similar to that of the control samples as shown by headspace SPME GC-MS analysis.

The lespedeza stalks with steam pretreatment were fermented to lactic acid by simultaneous saccharification and fermentation (SSF) in this study. Orthogonal design methodology was used to evaluate the optimum SSF conditions that give maximum lactic acid yield. We have investigated the following relative factors, such as temperature, loading of cellulase, calcium carbonate and concentration of substrate. The optimum operating conditions were found to be temperature of 43 °C, cellulase loading of 30 FPU/g substrate, calcium carbonate of 3 % and substrate of 6 %. Comparisons of different steam pretreated conditions on lactic acid yield from lespedeza stalks were also made. The results showed that lactic acid yields from lespedeza stalks with 4 min pretreatment at pressure of 1.0, 1.25, 1.5 and 2.0 Mpa were 41.8 %, 42.5 %, 50.6 % and 64.0 % of the theoretical, respectively. The lactic acid yield from steam pretreated lespedeza stalks was much higher than that of lespedeza stalks without pretreatment (23.9 %). It can be concluded that the lactic acid yield was remarkably improved by steam pretreatment. The yield of lactic acid from steam pretreated lespedeza stalks was 1.68 times higher than that of untreated ones. Additionally, the lactic acid yield could be further promoted from 64.0 % to 89.4 % by washing pretreated stalks with water, which suggested that water processing is a promising method to remove inhibitors in broth to improve lactic acid yield.

Treatment of corn stover with aqueous ammonia removes most of the structural lignin, whereas retaining the majority of the carbohydrates in the solids. After treatment, both the cellulose and hemicellulose in corn stover become highly susceptible to enzymatic digestion. In this study, corn stover treated by aqueous ammonia was investigated as the substrate for lactic acid production by simultaneous saccharification and cofermentation (SSCF). A commercial cellulase (Spezyme-CP) and Lactobacillus pentosus American Type Culture Collection (ATCC) 8041 (Spanish Type Culture Collection [CECT]-4023) were used for hydrolysis and fermentation, respectively. In batch SSCF operation, the carbohydrates in the treated corn stover were converted to lactic acid with high yields, the maximum lactic acid yield reaching 92% of the stoichiometric maximum based on total fermentable carbohydrates (glucose, xylose, and arabinose). A small amount of acetic acid was also produced from pentoses through the phosphoketolase pathway. Among the major process variables for batch SSCF, enzyme loading and the amount of yeast extract were found to be the key factors affecting lactic acid production. Further tests on nutrients indicated that corn steep liquor could be substituted for yeast extract as a nitrogen source to achieve the same lactic acid yield. Fed-batch operation of the SSCF was beneficial in raising the concentration of lactic acid to a maximum value of 75.0 g/L.

Statistical optimization of simultaneous saccharification and l(+)-lactic acid fermentation from cassava bagasse using mixed culture of lactobacilli by response surface methodology

Amelioration of lactic acid production from cheese whey using micro-aeration

Comparison of the Production of Lactic Acid by Three Different Lactobacilli and its Recovery by Extraction and Electrodialysis