Fermentative Production Of Lactic Acid Research Articles

Life cycle assessment of fermentative production of lactic acid from bread waste based on process modelling using pinch technology

Bread waste (BW), a rich source of fermentable carbohydrates, has the potential to be a sustainable feedstock for the production of lactic acid (LA). In our previous work, the LA concentration of 155.4 g/L was achieved from BW via enzymatic hydrolysis, which was followed by a techno-economic analysis of the bioprocess. This work evaluates the relative environmental performance of two scenarios - neutral and low pH fermentation processes for polymer-grade LA production from BW using a cradle-to-gate life cycle assessment (LCA). The LCA was based on an industrial-scale biorefinery process handling 100 metric tons BW per day modelled using Aspen Plus. The LCA results depicted that wastewater from anaerobic digestion (AD) (42.3–51 %) and cooling water utility (34.6–39.5 %), majorly from esterification, were the critical environmental hotspots for LA production. Low pH fermentation yielded the best results compared to neutral pH fermentation, with 11.4–11.5 % reduction in the overall environmental footprint. Moreover, process integration by pinch technology, which enhanced thermal efficiency and heat recovery within the process, led to a further reduction in the impacts by 7.2–7.34 %. Scenario and sensitivity analyses depicted that substituting ultrapure water with completely softened water and sustainable management of AD wastewater could further improve the environmental performance of the processes.

Advanced Fermentation Techniques for Lactic Acid Production from Agricultural Waste

Lactic acid plays an important role in industrial applications ranging from the food industry to life sciences. The growing demand for lactic acid creates an urgent need to find economical and sustainable substrates for lactic acid production. Agricultural waste is rich in nutrients needed for microbial growth. Fermentative production of lactic acid from non-food-competing agricultural waste could reduce the cost of lactic acid production while addressing environmental concerns. This work provided an overview of lactic acid fermentation from different agricultural wastes. Although conventional fermentation approaches have been widely applied for decades, there are ongoing efforts toward enhanced lactic acid fermentation to meet the requirements of industrial productions and applications. In addition, agricultural waste contains a large proportion of pentose sugars. Most lactic-acid-producing microorganisms cannot utilize such reducing sugars. Therefore, advanced fermentation techniques are also discussed specifically for using agricultural waste feedstocks. This review provides valuable references and technical supports for the industrialization of lactic acid production from renewable materials.

Lactic Acid: A Comprehensive Review of Production to Purification

Lactic acid (LA) has broad applications in the food, chemical, pharmaceutical, and cosmetics industries. LA production demand rises due to the increasing demand for polylactic acid since LA is a precursor for polylactic acid production. Fermentative LA production using renewable resources, such as lignocellulosic materials, reduces greenhouse gas emissions and offers a cheaper alternative feedstock than refined sugars. Suitable pretreatment methods must be selected to minimize LA cost production, as the successful hydrolysis of lignocellulose results in sugar-rich feedstocks for fermentation. This review broadly focused on fermentative LA production from lignocellulose. Aspects discussed include (i). low-cost materials for fermentative LA production, (ii). pretreatment methods, (iii). enzymatic hydrolysis of cellulose and hemicellulose, (iv). lactic acid-producing microorganisms, including fungi, bacteria, genetically modified microorganisms, and their fermentative pathways, and (v). fermentation modes and methods. Industrial fermentative lactic acid production and purification, difficulties in using lignocellulose in fermentative LA production, and possible strategies to circumvent the challenges were discussed. A promising option for the industrial production and purification of LA that contains enzyme and cell recycling continuous simultaneous saccharification and fermentation coupled with membrane-based separation was proposed. This proposed system can eliminate substrate-, feedback-, and end-product inhibition, thereby increasing LA concentration, productivity, and yield.

H2 O2 feeding enables LPMO-assisted cellulose saccharification during simultaneous fermentative production of lactic acid.

Simultaneous saccharification and fermentation (SSF) is a well-known strategy for valorization of lignocellulosic biomass. Because the fermentation process typically is anaerobic, oxidative enzymes found in modern commercial cellulase cocktails, such as lytic polysaccharide monooxygenases (LPMOs), may be inhibited, limiting the overall efficiency of the enzymatic saccharification. Recent discoveries, however, have shown that LPMOs are active under anoxic conditions if they are provided with H2 O2 at low concentrations. In this study, we build on this concept and investigate the potential of using externally added H2 O2 to sustain oxidative cellulose depolymerization by LPMOs during an SSF process for lactic acid production. The results of bioreactor experiments with 100 g/L cellulose clearly show that continuous addition of small amounts of H2 O2 (at a rate of 80 µM/h) during SSF enables LPMO activity and improves lactic acid production. While further process optimization is needed, the present proof-of-concept results show that modern LPMO-containing cellulase cocktails such as Cellic CTec2 can be used in SSF setups, without sacrificing the LPMO activity in these cocktails.

High-Level fermentative production of Lactic acid from bread waste under Non-sterile conditions with a circular biorefining approach and zero waste discharge

Bread waste (BW) is a severe solid waste management problem in Europe. The current study demonstrates an environment-friendly solution by valorising BW into lactic acid (LA) and the corresponding solid residues generated during hydrolysis and fermentation to biogas. To this end, BW was saccharified through acidic and enzymatic hydrolysis, and the hydrolysate obtained was used for LA fermentation under non-sterile conditions using thermophilic Bacillus coagulans DSM1. Maximum glucose concentration achieved during acid hydrolysis with 2% (v/v) acid loading and 20% (w/v) solid loading was 67.9 g/L glucose, with a yield of 0.34 g/g BW. The LA accumulated with concentrated BW acid hydrolysate was 102.4 g/L with yield and productivity of 0.75 g/g and 1.42 g/L. h, respectively. For enzymatic hydrolysis, three commercial amylase preparations (Amyloglucosidase, Spirizyme, Dextrozyme) were employed. The highest glucose release (98.6 g/L) and yield (0.49 g glucose/g BW) was attained with Dextrozyme from Novozymes. The fed-batch fermentation by B. coagulans was conducted, using commercial glucose and glucose-rich BW hydrolysate from Dextrozyme. The LA titer, yield and productivity obtained with pure glucose were 222.7 g/L, 0.92 g/g and 1.86 g/L.h, respectively, whereas BW hydrolysate (BWH) resulted in 155.4 g/L LA, with a conversion yield and productivity of 0.85 g/g glucose and 1.30 g/L. h, respectively. Further to the LA biosynthesis, the solid residues generated during hydrolysis and fermentation were subjected to biogas generation, resulting in 553 mL CH4/g volatile solids under batch mode. This massive LA titer amassed under non-sterile conditions and integrated biogas production using fermented residues demonstrates a high potential for an integrated biorefinery based on BW.

Enhanced fermentative lactic acid production from source-sorted organic household waste: Focusing on low-pH microbial adaptation and bio-augmentation strategy

Lactic acid (LA) production at low pH could significantly reduce the need for neutralizing agents, leading to reduction of operational costs. In the present study, LA production at acidic conditions was investigated using source-sorted organic household waste (SSOHW). Controlling the pH at low value (i.e. 5.0) and bio-augmenting with Pediococcus acidilactici led to a concentration of 39.3 ± 0.5 g-LA/L with a yield of 0.75 ± 0.02 g-LA/g-sugar. In contrast, secondary fermentation at higher pH level (i.e. 5.5 and 6.0) resulted in complete LA degradation. Subsequently, consecutive batch fermentations were conducted to adapt P. acidilactici to SSOHW and improve the LA production. Results showed that P. acidilactici could successively adapt in the SSOHW reaching a relative abundance above 2.8% at adaptation process. The added P. acidilactici ensured a high concentration of LA at three consecutive generations, achieving an increment above 18% compared to control test (abiotic augmentation). Moreover, adaptation processes (i.e. maintaining pH at 4.0 or stepwise decreasing the pH from 5.0 to 4.0) significantly improved LA concentration and productivity at the pH of 4.0. Overall, the results provide a promising method to reduce the LA production costs using residual resources.

Fermentative lactic acid production from seaweed hydrolysate using Lactobacillus sp. And Weissella sp

Lactic acid (LA) is an essential commodity chemical, with bio-based LA ruling the market share. Macroalgae are a desirable feedstock for LA fermentation due to their high carbohydrate and low lignin content. Ulva sp., Gracilaria sp., and Sargassum cristaefolium were evaluated as a feedstock for LA fermentation. Mild acid-thermal hydrolysis (sulfuric acid concentrations < 5%) resulted in superior reducing sugar recovery. Gracilaria sp. attained maximum reducing sugar recovery (0.39 g/g biomass) and lactate yield (0.94 g/g). LA fermentation of fucose-rich hydrolysate of Sargassum cristaefolium is demonstrated for the first time, with 0.81 g/g LA yield and 0.36 g/g reducing sugars. Ulva sp. attained 0.21 g/g reducing sugars and 0.85 g/g LA yield. The efficiency of macroalgae for lactate bioconversion was in the order: red macroalgae > green macroalgae > brown macroalgae. L. rhamnosus and L. plantarum could efficaciously utilize seaweed sugars for LA production. Macroalgae can potentially replace lignocellulosic biomass as a feedstock in LA fermentation.

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

This study reports for lactic acid production from different carbohydrates; monosaccharide (glucose, galactose, lactose) & disaccharides (sucrose) and from lignocellulose biomass (rice straw) by a novel strain ‘Lactobacillus sp. strain TERI-D3’. ‘TERI-D3’ strain produced 19.9, 19.4, 18.1 and 15.8 ​g/L of lactic acid from glucose, sucrose, lactose and galactose, respectively. Maximum lactic acid yield efficiency (0.97 ​g/g) was observed with glucose (>95% of the theoretical maximum yield). Lactic acid titer from glucose was 0.41 ​g/L. The lactic acid titer and yield from rice straw biomass sugar was; 11.58 ​g/L and 0.73 ​g/g (>80% of the theoretical maximum yield), respectively. The novelty of this study is that the ‘TERI-D3’ strain is a promising microbe for green lactic acid as it has potential to valorize cheese industry waste, algae biomass as well as to utilize inexpensive next generation lignocellulose biomass that are abundant and do not compete with food chain supply. This approach of recycling and or reuse of organic waste holds importance in the circular economy frame.

Impact of storage duration and micro-aerobic conditions on lactic acid production from food waste

Food waste (FW) is an abundant resource with great potential for lactic acid (LA) production. In the present study, the effect of storage time on FW characteristics and its potential for LA production was investigated. The largest part of sugars was consumed during 7 to 15 days of FW storage and the sugar consumption reached 68.0% after 15 days. To enhance the LA production, micro-aerobic conditions (13 mL air/g VS) and addition of β-glucosidase were applied to improve polysaccharides hydrolysis, resulting to increase of monosaccharides content to 76.6%. Regarding fermentative LA production, the highest LA titer and yield of hydrolyzed FW was 32.1 ± 0.5 g/L and 0.76 ± 0.01 g/g-sugar, respectively. Furthermore, L-LA isomer was higher than 70% when FW was stored for up to 7 days. However, attention should be paid on controlling the FW storage to approximately one week.

Elevated, non-proliferative temperatures change the profile of fermentation products in Corynebacterium glutamicum

Although temperature is a crucial factor affecting enzymatic activity on biochemical and biofuel production, the reaction temperature for the generation of these products is usually set at the optimal growth temperature of the host strain, even under non-proliferative conditions. Given that the production of fermentation products only requires a fraction of the cell's metabolic pathways, the optimal temperatures for microbial growth and the fermentative production of a target compound may be different. Here, we investigated the effect of temperature on lactic and succinic acids production, and related enzymatic activities, in wild-type and succinic acid-overproducing strains of Corynebacterium glutamicum. Interestingly, fermentative production of lactic acid increased with the temperature in wild-type: production was 69% higher at 42.5°C, a temperature that exceeded the upper limit for growth, than that at the optimal growth temperature (30°C). Conversely, succinic acid production was decreased by 13% under the same conditions in wild-type. The specific activity of phosphoenolpyruvate carboxylase decreased with the increase in temperature. In contrast, the other glycolytic and reductive TCA cycle enzymes demonstrated increased or constant activity as the temperature was increased. When using a succinic acid over-producing strain, succinic acid production was increased by 34% at 42.5°C. Our findings demonstrate that the profile of fermentation products is dependent upon temperature, which could be caused by the modulation of enzymatic activities. Moreover, we report that elevated temperatures, exceeding the upper limit for cell growth, can be used to increase the production of target compounds in C. glutamicum. KEY POINTS: • Lactate productivity was increased by temperature elevation. • Succinate productivity was increased by temperature elevation when lactate pathway was deleted. • Specific activity of phosphoenolpyruvate carboxylase was decreased by temperature elevation.

Poly(3-hydroxybutyrate) bioproduction in a two-step sequential process using wastewater

In the present study, a cheese whey agro-industrial byproduct was utilized as a natural feedstock for bioplastic production. The bioprocess consisted of a fermentative lactic acid production (step 1) and a following photofermentative poly(3-hydroxybutyrate) production (step 2). During step 1, the bacterium Lactobacillus sp. converted lactose (contained in cheese whey) into lactic acid. During step 2, the marine bacterium Rhodovulum sulfidophilum DSM-1374 converted lactic acid, contained in the cheese-whey fermented effluent (CWFE), in bioplastic. In this investigation, the CWFE produced during step 1 showed a lactic acid content of 29.5 ± 1.3 g/L. When, for feeding Rhodovulum sulfidophilum DSM-1374, was utilized CWFE diluted with water (50 %, v/v) the highest poly(3-hydroxybutyrate) content (67 ± 3.1 % of bacterial dry-biomass) was observed. Both bioprocess steps can significantly contribute to realize a circular bioeconomy able to cut down the costs of bioplastic production and reduce the environmental impact caused by the intensive human feed and food productions.

Fermentative Production of Lactic Acid as a Sustainable Approach to Valorize Household Bio-Waste

Source-sorted organic portion of municipal solid waste (bio-waste) can be fermented to lactic acid, a platform chemical widely used in the production of biodegradable polymers, green solvents and chemicals. In the present study, fermentation of bio-waste using lactic acid producing bacterium (LAB) Lactobacillus delbrueckii was investigated. Results showed that adding 10% (v/v) of L. delbrueckii as LAB inoculum along with pH adjustment to 6.2 had the highest lactic acid yield (0.65 g/g total sugars). Nevertheless, pH adjustment without bio-augmentation could also result in relatively high yield of lactic acid (0.57 g/g total sugars). Furthermore, enzymatic hydrolysis was applied to boost the lactic acid production slightly increasing the yield to 0.72 g/g total sugars. Thus, fermentative production of lactic acid can be achieved without the addition of enzymes to reduce production costs. Overall, the results indicate that bio-waste could be a suitable substrate for the production of lactic acid.

Bio-augmentation to improve lactic acid production from source-sorted organic household waste

The high and easy degradable sugar content of source-sorted organic household (SSOHW) suggests it as a promising candidate for fermentative lactic acid production. The present study aimed to apply bio-augmentation strategy with different lactic acid bacteria (Lactobacillus delbrueckii or Pediococcus acidilactici) to improve lactic acid production from non-sterile SSOHW. The optimum operational temperature, initial pH and total solid loading during fermentation were essential for lactic acid production. Lactic acid concentration of 20.7 ± 0.3 and 16.8 ± 0.4 g/L were obtained by bio-augmenting Pediococcus acidilactici and Lactobacillus delbrueckii, respectively, achieving an increment of 36.2% and 10.5% compared to abiotic augmentation. A lactic acid yield of 0.73 g/g-sugar was achieved with addition of Pediococcus acidilactici, while the optical purity of LA was also improved by the bio-augmentation. Furthermore, response surface methodology along with the Box-Behnken model was applied to determine the optimal operational conditions (i.e. temperature, initial pH and total solid loading). Based on the outcome, the highest concentration and yield were 31.2 g/L and 0.735 g/g-sugar at temperature of 32.4 °C, initial pH of 8.0 and total solid loading of 105.0 g/L. Finally, the predicted value was validated by scale-up experiment, and the LA titer and yield of scale-up fermenter were well corresponding to predicted value. The bio-augmentation strategy and process optimization provided a simple and energy saving method for industrial LA production from SSHOW. With respect to environmental sustainability and cleaner production, the conversion of bio-waste to lactic acid is an advantageous waste management approach that will contribute to the transition from a petro-based economy towards the production and use of bio-based derived products thereby creating innovative value chains with lower carbon footprint and social responsibility.

Comparison of Different Lactobacilli Regarding Substrate Utilization and Their Tolerance Towards Lignocellulose Degradation Products

Fermentative lactic acid production is currently impeded by low pH tolerance of the production organisms, the successive substrate consumption of the strains and/or the requirement to apply purified substrate streams. We identified Lactobacillus brevis IGB 1.29 in compost, which is capable of producing lactic acid at low pH values from lignocellulose hydrolysates, simultaneously consuming glucose and xylose. In this study, we compared Lactobacillus brevis IGB 1.29 with the reference strains Lactobacillus brevis ATCC 367, Lactobacillus plantarum NCIMB 8826 and Lactococcus lactis JCM 7638 with regard to the consumption of C5- and C6-sugars. Simultaneous conversion of C5- and C6-monosaccharides was confirmed for L. brevis IGB 1.29 with consumption rates of 1.6 g/(L h) for glucose and 1.0 g/(L h) for xylose. Consumption rates were lower for L. brevis ATCC 367 with 0.6 g/(L h) for glucose and 0.2 g/(L h) for xylose. Further trials were carried out to determine the sensitivity towards common toxic degradation products in lignocellulose hydrolysates: acetate, hydroxymethylfurfural, furfural, formate, levulinic acid and phenolic compounds from hemicellulose fraction. L. lactis was the least tolerant strain towards the inhibitors, whereas L. brevis IGB 1.29 showed the highest tolerance. L. brevis IGB 1.29 exhibited only 10% growth reduction at concentrations of 26.0 g/L acetate, 1.2 g/L furfural, 5.0 g/L formate, 6.6 g/L hydroxymethylfurfural, 9.2 g/L levulinic acid or 2.2 g/L phenolic compounds. This study describes a new strain L. brevis IGB 1.29, that enables efficient lactic acid production with a lignocellulose-derived C5- and C6-sugar fraction.

Is seashell powder suitable for phosphate recovery from fermentation broth?

This communication elaborates on the use of seashell powder (SP) for the removal of phosphate from lactic acid-containing fermentation broth. Despite extensive past research regarding the application of SP for phosphate removal from wastewater, no information is available for solutions containing various organic compounds. In order to fill this knowledge gap, tests were performed with pure phosphate solution (PPS) and PPS containing 0.83 M of three alcohols, ethanol, propanol or 1,2-propanediol, or 0.83 M of three organic acids, acetic, propionic or lactic acid. Furthermore, a real fermentation broth (RFB) obtained from the fermentative production of lactic acid from food waste was tested. Using 4.8 g SP, more than 95% of phosphate, present at an initial concentration of 50 mg L−1, could be removed from PPS and PPS containing alcohols after 120 min. The presence of organic acids reduced the removal capacity of SP and only 55%–73% of the phosphate initially present was removed. The presence of lactic acid also substantially affected the removal of phosphate from RFB when 132 mg L−1 phosphate was initially present: after 120 min, only 28.6 mg L−1 of phosphate had been removed. The results indicate the use of SP for phosphate removal from fermentation broth, contributing to multi-component utilization of fermentation broth. However, the effects of respective fermentation products on removal capacity should first be tested.

Technical and economic assessment of food waste valorization through a biorefinery chain

This work presents the economic assessment of an integrated biorefinery process for sequential fermentative production of lactic acid and biogas from food waste. The integrated biorefinery process was compared to single processes for either lactic acid or biogas production. The economic assessment, considering catchment areas from 2000 to 1 million inhabitants, was based on data from real biorefinery plants and carried out using SuperPro Designer® 8.0. The consistency of the approach was evaluated through a set of composite indicators. The integrated biorefinery process was investigated for its economic feasibility of producing lactic acid and biogas, the impact of process scale as well as energy use. Outcomes revealed that an integrated biorefinery process contributes more to optimal use of energy and material flows than single processes. Profitability was confirmed for catchment areas larger than 20,000–50,000 inhabitants.

Parametric Optimization of Lactic Acid Production by Immobilized Lactobacillus casei Using Box-Behnken Design

Technological optimization of process parameters posses one of the open challenge for fermentative lactic acid (LA) production. Hence optimization of process parameters viz. sugar concentration, pH, biomass, incubation temperature and incubation time for maximizing fermentative lactic acid production from molasses sugar and corn steep liquor as a low cost carbon and nitrogen source, respectively by immobilized Lactobacillus casei MTCC 1423 cells has been carried out using Box Behnken Design (BBD). By applying multiple regressions on experimental data, quadratic models have been realized, explaining role of each variable and their quadratic interaction on LA production, LA productivity and yield coefficient. Analysis of variance has demonstrated that models are significant. The maximum LA production (132 g/(L fermentor volume) ), LA productivity of 2.36 g/(L×h) and yield coefficient of 0.936 g/(g substrate) have been estimated by the quadratic regression model for optimum process parameters values of sugar concentration (194 g/L), pH (6.85), biomass (310 mg, CDW), incubation temperature (37°C) and incubation time (57 h). The optimization validated experiments had resulted in LA production of 130±2.1 g/(L fermentor volume) ; LA productivity of 2.28±0.037 g/(L×h) and yield coefficient of 0.921±0.003 g/(g substrate) and which are substantially higher than those obtained with free cells of Lb. casei MTCC 1423 (2%, v/v inoculums size) at obtained optimized process parameters values. Thus resulted quadratic models provided an opportunity for scaling up the lactic acid production process and demonstrated the economic potential of using agro industrial waste molasses sugar for lactic acid production by Lb. casei MTCC 1423.

A Comparison Study on the Production and Recovery of Lactic Acid by Fermenting Dairy By-Products with P. acidilactici and Lb. delbrüeckii spp. bulgaricus

This paper provides a comparative study on the fermentative production of lactic acid (LA) by the novel Pediococcus acidilactici KTU05-7, previously isolated from rye sourdough, and the common dairy Lactobacillus delbrueckii spp. bulgaricus using dairy by-products as a substrate. Lactic acid bacteria growth in different fermentation medium, β-d-galactosidase activity, lactose consumption, distribution of l(+)/d(−)-lactic acid isomers and LA purification using a system of membranes were also examined. The highest LA yield (1.9 g/g) was obtained fermenting the whey permeate for 24 h with the novel P. acidilactici. This strain also showed a better growth in whey permeate, a higher tolerance to low pH conditions and tended to produce mainly l(+)-lactic acid, compared to the standard L. bulgaricus. Furthermore, the proteolytic action of P. acidilactici simplified the membrane filtration procedure, and hindered the formation of protein aggregate in fermented broth as compared to L. bulgaricus. The findings of this research suggest that the Pediococcus acidilactici strain has a potential to improve the biotechnological production of LA from dairy industry waste and its recovery by membrane processes.

Characterization of a heat-tolerant Chlorella sp. GD mutant with enhanced photosynthetic CO2 fixation efficiency and its implication as lactic acid fermentation feedstock

BackgroundFermentative production of lactic acid from algae-based carbohydrates devoid of lignin has attracted great attention for its potential as a suitable alternative substrate compared to lignocellulosic biomass.ResultsA Chlorella sp. GD mutant with enhanced thermo-tolerance was obtained by mutagenesis using N-methyl-N′-nitro-N-nitrosoguanidine to overcome outdoor high-temperature inhibition and it was used as a feedstock for fermentative lactic acid production. The indoor experiments showed that biomass, reducing sugar content, photosynthetic O2 evolution rate, photosystem II activity (Fv/Fm and Fv′/Fm′), and chlorophyll content increased as temperature, light intensity, and CO2 concentration increased. The mutant showed similar DIC affinity and initial slope of photosynthetic light response curve (α) as that of the wild type but had higher dissolved inorganic carbon (DIC) utilization capacity and maximum photosynthesis rate (Pmax). Moreover, the PSII activity (Fv′/Fm′) in the mutant remained normal without acclimation process after being transferred to photobioreactor. This suggests that efficient utilization of incident high light and enhanced carbon fixation with its subsequent flux to carbohydrates accumulation in the mutant contributes to higher sugar and biomass productivity under enriched CO2 condition. The mutant was cultured outdoors in a photobioreactor with 6% CO2 aeration in hot summer season in southern Taiwan. The harvested biomass was subjected to separate hydrolysis and fermentation (SHF) for lactic acid production with carbohydrate concentration equivalent to 20 g/L glucose using the lactic acid-producing bacterium Lactobacillus plantarum 23. The conversion rate and yield of lactic acid were 80% and 0.43 g/g Chlorella biomass, respectively.ConclusionsThese results demonstrated that the thermo-tolerant Chlorella mutant with high photosynthetic efficiency and biomass productivity under hot outdoor condition is an efficient fermentative feedstock for large-scale lactic acid production.

Utilization of Date Juice for the Production of Lactic Acid by Streptococcus Thermophilus

The interest in the fermentative production of lactic acid has increased due to the prospects of environmental friendliness and of using renewable resources instead of petrochemicals. In this context, we have judged that is gainful to use the date juice which is with a low commercial value as a substrate for the production of lactic acid by Streptococcus thermophilus. Further, dates are rich in sugar ranging from 65% to 80% on dry weight basis mostly of inverted form (glucose and fructose), which can used as carbon source for the fermentation and the production of microbial biomass. The parameters optimization for lactic acid production by S. thermophilus grown on medium based on dates in order to improve yields is applied in this study. The results showed that the maximum of lactic acid production (36.9g/l) is obtained after the enrichment of date juice with yeast extract (15%), Tween 80 (1g/l) MgSO4 (0.5g/l), MnSO4 (0.02g/l) and K2 HPO4 (1g/l).