Efficient d-lactic acid production from raw starch

Applied Microbiology and Biotechnology, 2007

The concept of utilizing excess biomass or wastes from agricultural and agro-industrial residues to produce energy, feeds or foods, and other useful products is not necessarily new. Recently, fermentation of biomass has gained considerable attention due to the forthcoming scarcity of fossil fuels and also due to the necessity of increasing world food and feed supplies. A cost-effective viable process for lactic acid production has to be developed for which several attempts have been initiated. Fermentation techniques result in the production of either D (−) or L (+) lactic acid, or a racemic mixture of both, depending on the type of organism used. 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. Amylolytic bacteria Lactobacillus amylovorus ATCC 33622 is reported to have the efficiency of full conversion of liquefied cornstarch to lactic acid with a productivity of 20 g l −1 h −1 . A maximum of 35 g l −1 h −1 was reported using a high cell density of L. helveticus (27 g l −1 ) with a complete conversion of 55-to 60-g l −1 lactose present in whey. Simultaneous saccharification and fermentation is proved to be best in the sense of high substrate concentration in lower reactor volume and low fermentation cost. In this review, a survey has been made to see how effectively the fermentation technology explored and exploited the cheaply available source materials for value addition with special emphasis on lactic acid production.

Journal of Industrial Microbiology, 1991

An alternative process for industrial lactic acid production was developed using a starch degrading lactic acid producing organism, Lactobacillus amylovorus B-4542. In this process, saccharification takes place during the fermentation, eliminating the need for complete hydrolysis of the starch to glucose prior to fermentation. The cost savings of this alternative are substantial since it eliminates the energy input, separate reactor tank, time, and enzyme associated with the typical pre-fermentation saccharification step. The only pre-treatment was gelatinization and enzyme-thinning of the starch to overcome viscosity problems associated with high starch concentrations and to make the starch more rapidly degradable. This fermentation process was optimized for temperature, substrate level, nitrogen source and level, mineral level, B-vitamins, volatile fatty acids, pH, and buffer source. The rate of the reaction and the final level of lactic acid obtained in the optimized liquefied starch process was similar to that obtained with L. delbrueckii B-445 using glucose as the substrate.

Journal of Scientific & Industrial Research

Lactic acid is widely used in the food, cosmetic, pharmaceutical, and chemical industries and has received increased attention for use as a monomer for the production of biodegradable poly (lactic acid). It can be produced by either biotechnological fermentation or chemical synthesis, but the former route has received considerable interest recently, due to environmental concerns and the limited nature of petrochemical feedstocks. The objective of this study was to produce lactic acid from Brewery Spent Grain by using lactobacillus plantarum. The production process was carried out in four main stages, such as pretreatment, hydrolysis, fermentation and recovery of lactic acid. Brewery spent grain was dried using oven at 80ºC temperature for 24 hr. Then for the hydrolysis, Box Behnken Design (BBD) was applied to investigate the effect of temperature (115-130ºC), reaction time (25-35min) and acid concentration (1.5-2M) using Design expert® 7 software. RSM was applied to investigate the interaction effect of the hydrolysis process variables and to find the optimum yield of lactic acid from BSG. After hydrolysis process, reducing sugar content of the hydrolyzate was quantified using quantitative benedict reagent solution. Fermentation of the hydrolyzate was performed using 150mL, Lactobacillus plantarum at 35ºC temperature, pH 5.0-5.5 and 200 rpm for 72hrs fermentation time for all samples. After fermentation recovery of lactic acid and purification process was carried out by centrifuging all samples at 5000 rpm for 5 min followed by filtration through 0.2μm paper filter. The concentration of lactic acid was determined by titration of the sample using 4M of sodium hydroxide. Significance of the process variables were analyzed using analysis of variance (ANOVA) and second order polynomial function was fitted to the experimental results. Thus, the influence of all experimental variables, factors and interaction effects on the response was investigated. Hydrolysis temperature, time, sulfuric acid concentration and interaction between reaction temperature and sulfuric acid concentration have significant effect on the yield of lactic acid. RSM optimization yielded the best yield of total reducing sugar and the maximum yield of lactic acid were obtained at 129.75ºC, 32.39 min and 1.89M. Under these condition 53.07% and 26.71% per 150ml of hydrolysate of total reducing sugar and lactic acid was obtained respectively. iii ACKNOWLEDGMENTS I would like to thank the Almighty GOD for giving me the strength and wisdom to successfully complete this thesis for his protection and strength, and an ever present helps in the entire situation and challenge that I face. Moreover, I would like to express my heartfelt appreciation and thank to my Instructor and now this thesis research Advisor Dr.S.Anuradha Jabasingh (Assoc. Professor), for her sustainable and appreciable guidance, tireless advising, for sharing her knowledge, skill, experience and adjustment starting from the development of proposal up to the successful completion of this thesis.

Journal of Applied Biotechnology & Bioengineering

background: Lactic acid (LA) is a carboxylic acid widely used as preservative, acidulant, and/or flavouring in food industry; it is also used as a raw material for the production of lactate ester, propylene glycol, 2,3-pentanedione, propanoic acid, acrylic acid and acetaldehyde. In recent years, the demand for LA production has dramatically increased due to its application as a monomer for poly-lactic acid synthesis, a biodegradable polymer used as a plastic in many industrial applications. LA can be produced either by fermentation or chemical synthesis; the former route has received considerable interest, due to environmental concerns and the limited nature of petrochemical feedstocks; thus, 90% of LA produced worldwide is obtained by fermentation, this process comprises the bioconversion of a sugar solution (carbohydrates) into LA in the presence of a microorganism. Objectives: This work is aimed at studying the effect of pH control and culture media composition on the LA production using renewable sources from the agroindustry sector. Methods: A Lactobacillus brevis strain is used to perform lab scale experiments under aerobic and anaerobic conditions, using three different culture media compositions: a high nutritional content medium (MRS), as a reference, a low nutritional content medium with glucose as the only carbon source (GM), and a potential low nutritional content medium with cassava flour as carbon source (HY1). results: The higher LA production is accomplished under anaerobic conditions, 17.6 ± 0.1, 12.6 ± 0.2 y 13.6 ± 0.2 g LA/L, for MRS, GM and HY1 medium, respectively. The effect of pH on LA biosynthesis in a 5L bioreactor is also studied using the HY1 medium. For a fermentation time of 120 h, the highest LA concentration obtained was 24.3 ± 0.7g LA/L, productivity 0.20 g/L/h, Y P/S 0.32g LA/g syrup, at pH 6.5. conclusions: These results are comparable with those using expensive carbon sources such as glucose, and show cassava flour as a promising low-cost substrate source for lab and eventually large scale LA biosynthesis.

Applied Biochemistry and Biotechnology, 2003

Conversion of food wastes into lactic acid by simultaneous saccharification and fermentation (SSF) was investigated. The process involves saccharification of the starch component in food wastes by a commercial amylolytic enzyme preparation (a mixture of amyloglucosidase, α-amylase, and protease) and fermentation by Lactobacillus delbrueckii. The highest observed overall yield of lactic acid in the SSF was 91% of theoretical. Lactic acid concentration as high as 80 g/L was attainable in 48 h of the SSF. The optimum operating conditions for the maximum productivity were found to be 42°C and pH 6.0. Without supplementation of nitrogen-containing nutrients, the lactic acid yield in the SSF decreased to 60%: 27 g/L of lactic acid from 60 g/L of food waste. The overall performance of the SSF, however, was not significantly affected by the elimination of mineral supplements.

Applied and Environmental Microbiology, 2009

In order to achieve direct and efficient fermentation of optically pure D-lactic acid from raw corn starch, we constructed L-lactate dehydrogenase gene (ldhL1)-deficient Lactobacillus plantarum and introduced a plasmid encoding Streptococcus bovis 148 ␣-amylase (AmyA). The resulting strain produced only D-lactic acid from glucose and successfully expressed amyA. With the aid of secreting AmyA, direct D-lactic acid fermentation from raw corn starch was accomplished. After 48 h of fermentation, 73.2 g/liter of lactic acid was produced with a high yield (0.85 g per g of consumed sugar) and an optical purity of 99.6%. Moreover, a strain replacing the ldhL1 gene with an amyA-secreting expression cassette was constructed. Using this strain, direct D-lactic acid fermentation from raw corn starch was accomplished in the absence of selective pressure by antibiotics. This is the first report of direct D-lactic acid fermentation from raw starch.

The sequential production of bioethanol and lactic acid from starch materials and lignocellulosic materials was investigated as ethanol fermentation broth (EFB) can provide nutrients for lactic acid bacteria. A complete process was developed, and all major operations are discussed, including ethanol fermentation, broth treatment, lactic acid fermentation, and product separation. The effect of process parameters, including ethanol fermentation conditions, treatment methods, and the amount of EFB used in simultaneous saccharification and fermentation (SSF), is investigated. Under the selected process conditions, the integrated process without additional chemical consumption provides a 1.08 acid/alcohol ratio (the broth containing 22.4 g/L ethanol and 47.6 g/L lactic acid), which corresponds to a polysaccharide utilization ratio of 86.9 %. Starch ethanol can thus promote cellulosic lactic acid by providing important nutrients for lactic acid bacteria, and in turn, cellulosic lactic acid could promote starch ethanol by improving the profit of the ethanol production process. Two process alternatives for the integration of starch ethanol and cellulosic lactic acid are compared, and some suggestions are given regarding the reuse of yeast following the cellulosic SSF step for lactic acid production.

Chemical Engineering Journal, 2012

An experimental study was carried out for the corn cobs thermal conversion to obtain the maximum content in lactic acid. For this purpose, under the same conditions (275 • C and 30 min) different concentrations of Ca(OH) 2 as alkaline catalyst were used (from 0.32 M to 1 M). The maximum content of lactic acid (6.72 ± 0.31 g/L) was obtained with 0.7 M of Ca(OH) 2 . With this catalyst concentration, different reaction conditions were used (250, 275 and 300 • C and 15, 30 and 45 min). The optimal conditions to produce the highest yield of lactic acid from corn cobs in alkaline conditions were determined at 300 • C and 30 min, achieving 44.76 ± 2.59% respect to the total cellulose and hemicellulose contained in the initial corn cobs (7.38 ± 0.43 g/L of lactic acid).

International Journal of Hydrogen Energy, 2008

Batch and continuous tests were conducted to evaluate fermentative hydrogen production from starch (at a concentration of chemical oxygen demand (COD) 20 g/L) at 35 1C by a natural mixed culture of paper mill wastewater treatment sludge. The optimal initial cultivation pH (tested range 5-7) and substrate concentration (tested range 5-60-gCOD/L) were evaluated by batch reactors while the effects of hydraulic retention time (HRT) on hydrogen production, as expressed by hydrogen yield (HY) and hydrogen production rate (HPR), were evaluated by continuous tests. The experimental results indicate that the initial cultivation pH markedly affected HY, maximum HPR, liquid fermentation product concentration and distribution, butyrate/acetate concentration ratio and metabolic pathway. The optimal initial cultivation pH was 5.5 with peak values of HY 1.1 mol-H 2 /mol-hexose maximum HPR 10.4 mmol-H 2 /L/h and butyrate concentration 7700 mg-COD/L. In continuous hydrogen fermentation, the optimal HRT was 4 h with peak HY of 1.5 mol-H 2 /mol-hexose, peak HPR of 450 mmol-H 2 /L/d and lowest butyrate concentration of 3000 mg-COD/L. The HPR obtained was 280% higher than reported values. A shift in dominant hydrogen-producing microbial population along with HRT variation was observed with Clostridium butyricum, C. pasteurianum, Klebshilla pneumoniae, Streptococcus sp., and Pseudomonas sp. being present at efficient hydrogen production at the HRTs of 4-6 h. Strategies based on the experimental results for optimal hydrogen production from starch are proposed.