Lactic acid production from enzyme-thinned corn starch usingLactobacillus amylovorus

Isolation and Characterization of Pediococcus sp. HLV1 from Fermented Idly Batter

The aim of the present study is the isolation and characterization of the lactic acid bacteria from idly batter, a traditional Indian fermented product. To achieve the aim, 10 idly batter samples were selected from different regions of Kadapa district. In the primary isolation and screening process, 50 lactic-acid-producing bacteria were isolated, and from them, six strains were selected based on their lactic acid yielding capacity for further evaluation. The selected cultures were studied for their phenotypic characters, and all cultures were Gram positive, cocci, and catalase negative. All the six strains were tested for their growth and lactic acid production at above 35 °C, and finally, one strain that showed good growth at 50 °C was selected for further characterization. Molecular characterization by 16S rRNA gene analysis and BLAST analysis revealed 99% similarity with Pediococcus pentosaceus Ni1142. The isolated culture was named as Pediococcus sp. HLV1, and the sequence was submitted to the NCBI databank as accession number MH921241. The isolated strain is able to utilize a wide range of carbohydrate substrates including glucose, fructose, sucrose, lactose, maltose, and xylose. The major fermentation product from glucose is lactic acid. Pediococcus sp. HLV1 showed optimum growth and production of lactic acid with glucose as carbon source (10%) and yeast extract as nitrogen source (0.3%) at pH 7.0 and 40 °C. As well-known probiotic bacteria, the isolated Pediococcus spp. also showed antimicrobial activity against both Gram-positive and Gram-negative bacteria and more specifically inhibited Gram-positive Bacillus. Using the above optimal conditions, lactic acid from a fresh mango peel extract was studied, and at the end of the fermentation, 5.2% (v/v) of lactic acid was produced. In conclusion, the isolated LAB Pediococcus sp. strain HLV1 is able to grow and produce lactic acid at a high temperature (45 °C) and to survive at 50 °C. Mango peel, a by-product of mango pulp industries, can be utilized as one of the economically cheap feedstocks for industrial production of lactic acid by the Pediococcus sp. strain HLV1.

Production of Lactic Acid from Seaweed Hydrolysates via Lactic Acid Bacteria Fermentation

Biodegradable polylactic acid material is manufactured from lactic acid, mainly produced by microbial fermentation. The high production cost of lactic acid still remains the major limitation for its application, indicating that the cost of carbon sources for the production of lactic acid has to be minimized. In addition, a lack of source availability of food crop and lignocellulosic biomass has encouraged researchers and industries to explore new feedstocks for microbial lactic acid fermentation. Seaweeds have attracted considerable attention as a carbon source for microbial fermentation owing to their non-terrestrial origin, fast growth, and photoautotrophic nature. The proximate compositions study of red, brown, and green seaweeds indicated that Gracilaria sp. has the highest carbohydrate content. The conditions were optimized for the saccharification of the seaweeds, and the results indicated that Gracilaria sp. yielded the highest reducing sugar content. Optimal lactic acid fermentation parameters, such as cell inoculum, agitation, and temperature, were determined to be 6% (v/v), 0 rpm, and 30 °C, respectively. Gracilaria sp. hydrolysates fermented by lactic acid bacteria at optimal conditions yielded a final lactic acid concentration of 19.32 g/L.

Nitrogen Fertilizer Amendment Alter the Bacterial Community Structure in the Rhizosphere of Rice (Oryza sativa L.) and Improve Crop Yield

Availability of nitrogen (N) in soil changes the composition and activities of microbial community, which is critical for the processing of soil organic matter and health of crop plants. Inappropriate application of N fertilizer can alter the rhizosphere microbial community and disturb the soil N homeostasis. The goal of this study was to assess the effect of different ratio of N fertilizer at various early to late growth stages of rice, while keeping the total N supply constant on rice growth performance, microbial community structure, and soil protein expression in rice rhizosphere. Two different N regimes were applied, i.e., traditional N application (NT) consists of three sessions including 60, 30 and 10% at pre-transplanting, tillering and panicle initiation stages, respectively, while efficient N application (NF) comprises of four sessions, i.e., 30, 30, 30, and 10%), where the fourth session was extended to anthesis stage. Soil metaproteomics combined with Terminal Restriction Fragment Length Polymorphism (T-RFLP) were used to determine the rhizosphere biological process. Under NF application, soil enzymes, nitrogen utilization efficiency and rice yield were significantly higher compared to NT application. T-RFLP and qPCR analysis revealed differences in rice rhizosphere bacterial diversity and structure. NF significantly decreased the specific microbes related to denitrification, but opposite result was observed for bacteria associated with nitrification. Furthermore, soil metaproteomics analysis showed that 88.28% of the soil proteins were derived from microbes, 5.74% from plants, and 6.25% from fauna. Specifically, most of the identified microbial proteins were involved in carbohydrate, amino acid and protein metabolisms. Our experiments revealed that NF positively regulates the functioning of the rhizosphere ecosystem and further enabled us to put new insight into microbial communities and soil protein expression in rice rhizosphere.

The effect of adaptation of Lactobacillus amylovorus to increasing concentrations of sweet potato starch on the production of lactic acid for its potential use in the treatment of cannery waste

Lactobacillus amylovorus, an amylolytic species, was cultured in increasing concentrations of sweet potato starch to test the effect of this progressive acclimation on lactic acid production. This research is part of a project on the use of the waste stream from a sweet potato cannery to produce lactic acid. The media used for this acclimation was a modified version of the de Man, Rogosa and Sharpe medium, in which glucose was partially or totally substituted with sweet potato starch. The process was done in five steps, starting with 100% glucose in the first step and ending with 100% sweet potato starch in the last one. At each step, the effectiveness of the acclimation was tested by running fermentations with and without pH control for 62 h. The effect of the overall adaptation process was tested by comparing the growth and activity of the acclimated vs non-acclimated bacteria using sweet potato starch as the only source of carbohydrates. Growth and activity assessments indicated that L. amylovorus was able to ferment sweet potato starch into lactic acid. In most cases, pH control resulted in better substrate utilisation and larger amounts of lactic acid. In the comparison study, however, the adaptation process had a major influence on lactic acid production than the effect of pH. For 20 g L^-1 sweet potato starch media, adapted L. amylovorus under no pH control yielded 11.20 g L^-1 versus the non-adapted bacteria, which yielded 7.10 g L^-1. Under controlled pH conditions, 14.80 and 4.20 g L^-1 lactic acid were produced by adapted and non-adapted bacteria respectively.

Evaluation of emerging factors blocking filtration of high-adjunct-ratio wort

Corn starch has become a common adjunct for beer brewing in Chinese breweries. However, with increasing ratio of corn starch, problems like poor wort filtration performance arise, which will decrease production capacity of breweries. To solve this problem, factors affecting wort filtration were evaluated, such as the size of corn starch particle, special yellow floats formed during liquefaction of corn starch, and residual substance after liquefaction. The effects of different enzyme preparations including β-amylase and β-glucanase on filtration rate were also evaluated. The results indicate that the emerging yellow floats do not severely block filtration, while the fine and uniform-shape corn starch particle and its incompletely hydrolyzed residue after liquefaction are responsible for filtration blocking. Application of β-amylase preparation increased the filtration rate of liquefied corn starch. This study is useful for our insight into the filtration blocking problem arising in the process of high-adjunct-ratio beer brewing and also provides a feasible solution using enzyme preparations.

Supplementation of medium with diammonium hydrogen phosphate enhanced the D-lactate dehydrogenase levels leading to increased D-lactic acid productivity

The production of D-lactic acid by Lactobacillus lactis RM2-24 was investigated using modified media to increase the efficiency of the fermentation process. The results indicated that the addition of 5 g/l peptone and 1 g/l (NH4)2HPO4 enhanced D-lactic acid production by 32%, as compared to that obtained from non supplemented media, with a productivity of 3.0 g/l/h. Lactate dehydrogenase (LDH) expression profile in these different media was studied which resulted in appearance of additional LDH isoform produced by cells when they were grown in HSYE supplemented with (NH4)2HPO4. The additional LDH appears to be L-LDH contributing to production of L-lactic acid in the fermented broth. This is totally new information in the lactic acid fermentation and could be very useful to industries engaged in D-lactic acid production.

New trends and challenges in lactic acid production on renewable biomass

Lactic acid is a relatively cheap chemical with a wide range of applications: as a preservative and acidifying agent in food and dairy industry, a monomer for biodegradable poly-lactide polymers (PLA) in pharmaceutical industry, precursor and chemical feedstock for chemical, textile and leather industries. Traditional raw materials for fermentative production of lactic acid, refined sugars, are now being replaced with starch from corn, rice and other crops for industrial production, with a tendency for utilization of agro industrial wastes. Processes based on renewable waste sources have ecological (zero CO2 emission, eco-friendly by-products) and economical (cheap raw materials, reduction of storage costs) advantages. An intensive research interest has been recently devoted to develop and improve the lactic acid production on more complex industrial by-products, like thin stillage from bioethanol production, corncobs, paper waste, straw etc. Complex and variable chemical composition and purity of these raw materials and high nutritional requirements of Lare the main obstacles in these production processes. Media supplementation to improve the fermentation is an important factor, especially from an economic point of view. Today, a particular challenge is to increase the productivity of lactic acid production on complex renewable biomass. Several strategies are currently being explored for this purpose such as process integration, use of Lwith amylolytic activity, employment of mixed cultures of Land/or utilization of genetically engineered microorganisms. Modern techniques of genetic engineering enable construction of microorganisms with desired characteristics and implementation of single step processes without or with minimal pre-treatment. In addition, new bioreactor constructions (such as membrane bioreactors), utilization of immobilized systems are also being explored. Electrodialysis, bipolar membrane separation process, enhanced filtration techniques etc. can provide some progress in purification technologies, although it is still remaining the most expensive phase in the lactic acid production. A new approach of parallel production of lactic bacteria biomass with probiotic activity and lactic acid could provide additional benefit and profit rise in the production process.

Development and optimization of a culture medium for L-lactic acid production by Rhizopus oryzae using crude protein from dairy manure as a nitrogen source

Experiments were conducted using the crude protein in fresh dairy manure as the nitrogen source in the culture media for Rhizopus oryzae to produce L-lactic acid. Two uniform design experiments were carried out with one for optimizing seed culture while the other for best percent L-lactic acid production. Multiple linear regression and ANOVA analyses were employed to determine the most significant media components. Data from the first uniform design U6 (6(2)x 3), in which the experimental factors involved included nitrogen concentration (crude protein), spore concentration, and treatment duration, showed that the levels of these components in the optimal condition for the seed culture medium were 2.1 g/L nitrogen, 16 hour culture time, and 10(5) spore concentration. The biomass weight in the seed medium developed in this study reached 1.32 g/L, which was 48.3% higher than that of the control. The combination of culture time and nitrogen concentration was found to be most significant in influencing the biomass yield. In the second uniform design experiment, flask culture with five factors (glucose, nitrogen from dairy manure, ZnSO4, KH2PO4, and MgSO4) at eight levels was examined using the uniform design table U8 (8(5)) with the content of L-lactic acid as the evaluating response Y. The results showed that ZnSO4 had the most influence on L-lactic acid yield, followed by nitrogen and KH2PO4. The optimum culture medium in terms of lactic acid production consisted of 240 g/L glucose, 1.26 g/L crude protein, 1.05 g/L KH2PO4, and 0.25 g/L MnSO4, which could achieve a yield of 59.57% (7.1% higher than the control).

Amylolytic bacterial lactic acid fermentation — A review

Lactic acid, an enigmatic chemical has wide applications in food, pharmaceutical, leather, textile industries and as chemical feed stock. Novel applications in synthesis of biodegradable plastics have increased the demand for lactic acid. Microbial fermentations are preferred over chemical synthesis of lactic acid due to various factors. Refined sugars, though costly, are the choice substrates for lactic acid production using Lactobacillus sps. Complex natural starchy raw materials used for production of lactic acid involve pretreatment by gelatinization and liquefaction followed by enzymatic saccharification to glucose and subsequent conversion of glucose to lactic acid by Lactobacillus fermentation. Direct conversion of starchy biomass to lactic acid by bacteria possessing both amylolytic and lactic acid producing character will eliminate the two step process to make it economical. Very few amylolytic lactic acid bacteria with high potential to produce lactic acid at high substrate concentrations are reported till date. In this view, a search has been made for various amylolytic LAB involved in production of lactic acid and utilization of cheaply available renewable agricultural starchy biomass. Lactobacillus amylophilus GV6 is an efficient and widely studied amylolytic lactic acid producing bacteria capable of utilizing inexpensive carbon and nitrogen substrates with high lactic acid production efficiency. This is the first review on amylolytic bacterial lactic acid fermentations till date.

Fermentative production of lactic acid from biomass: an overview on process developments and future perspectives

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.

Production of L-lactic acid from fresh cassava roots slurried with tofu liquid waste by Streptococcus bovis

To reduce the production cost of biodegradable plastics, the fermentation performance of L-lactic acid for a new fermentation medium, fresh cassava roots (FCRs) as a substrate slurried with tofu liquid waste (TLW) as basal medium, was investigated by batch fermentation of Streptococcus bovis. The fermentation properties of the three substrates, namely, FCR, tapioca (cassava starch) and glucose, which were independently mixed with TLW, were compared with those independently mixed with the standard basal medium, trypto-soya broth (TSB). Experiments were conducted at various sugar concentrations of the substrates with CaCO(3) as a neutralizer. The maximum L-lactic acid concentrations (C(La)) obtained using the three substrates in TLW were about 75% of those obtained using TSB caused by less nutrients in the TLW. The L-lactic acid productivities (P(La)) and the specific growth rates of S. bovis (mu) in TLW were about 1/4 to 1/3 and 1/5 to 1/4 of those in TSB, respectively. The maximum C(La), P(La) and mu were obtained at 10% w/w sugar concentration. Total yields (eta) were nearly constant up to 10% w/w sugar concentration for TSB and TLW, that is, 80% to 85% and 50% to 60%, respectively. But their total yields decreased in more than 10% w/w sugar concentration in both basal media, because of substrate inhibition. The fermentation properties (C(La), P(La), mu, and eta) were found to be in the order of: FCR > tapioca > glucose for all concentrations of the three substrates. The fermentation properties for FCR and tapioca were higher than those for glucose, in TLW or TSB, because S. bovis in a medium containing starch (FCR and tapioca) has more amylase activity than in a medium containing glucose. The nutrients in FCR with poor nutrient basal medium (TLW) more strongly affected the fermentation properties than those in FCR with rich nutrient basal medium (TSB). The proposed fermentation medium of FCR slurried with TLW is worth studying in order to reduce production cost of biodegradable plastics.

A media design program for lactic acid production coupled with extraction by electrodialysis

The aim of this study was to investigate industrial media for lactic acid fermentation to reduce the cost of nitrogen sources. Corn steep liquor (CSL) was successfully used at 5% (v/v) in batch fermentations. Use of soluble CSL improved the productivity approximately 20% with an advantage of clearer fermentation broth. Yeast extract (YE)-complemented CSL media further increased the productivity. It was found that 3.1 g L(-1) yeast extract and 5% CSL could be an effective substitute for 15 g L(-1) yeast extract in 10% glucose medium. Spent brewery yeast was also used as a sole nitrogen source equivalent to 5% CSL. Lactic acid was recovered by electrodialysis from the cell free broth. Depleted cell free broth supplemented with 5 g L(-1) of yeast extract performed reasonably in batch cultures. Reuse of the fermentation broth may reduce the cost of raw materials as well as minimize the fermentation wastes.

Production ofD-Lactic Acid by Bacterial Fermentation of Rice Starch

D-Lactic acid was synthesized by the fermentation of rice starch using microorganisms. Two species: Lactobacillus delbrueckii and Sporolactobacillus inulinus were found to be active in producing D-lactic acid of high optical purity after an intensive screening test for D-lactic acid bacteria using glucose as substrate. Rice powder used as the starch source was hydrolyzed with a combination of enzymes: alpha-amylase, beta-amylase, and pullulanase to obtain rice saccharificate consisting of maltose as the main component. Its average gross yield was 82.5%. Of the discovered D-lactic acid bacteria, only Lactobacillus delbrueckii could ferment both maltose and the rice saccharificate. After optimizing the fermentation of the rice saccharificate using this bacterium, pilot scale fermentation was conducted to convert the rice saccharificate into D-lactic acid with a D-content higher than 97.5% in a yield of 70%. With this yield, the total yield of D-lactic acid from brown rice was estimated to be 47%, which is almost equal to the L-lactic acid yield from corn. The efficient synthesis of D-lactic acid can open a way to the large scale application of high-melting poly(lactic acid) that is a stereocomplex of poly(L-lactide) and poly(D-lactide). Schematic representation of the production of D-lactic acid starting from brown rice as described here.

Utilization for lactic acid production with a new acid hydrolysis of ram horn waste

The use of ram horn hydrolysate (RHH) as a substrate for lactic acid production was investigated using Lactobacillus casei. For this purpose, first RHH was produced. Ram horns were hydrolyzed by treating with acids (6N-H2SO4 and 6N-HCl) and neutralizing the solutions. The amounts of protein, nitrogen, ash, some minerals, total sugars, total lipids and amino acids of the RHH were determined. The effect of different concentrations (1-10% v/v) of RHH on the production of biomass, lactic acid concentration and sugar consumption was investigated, and a concentration of 6% RHH was found to be optimal. The content of lactic acid in the culture broth containing 6% RHH (44 g x l(-1)) for 26 h was 22% higher than that of the control culture broth (36 g x l(-1)). From this result, RHH was demonstrated to be a suitable supplement for lactic acid production, a use that would resolve a local environmental problem.

Comparison of isotopic fractionation in lactic acid and ethanol fermentations

Pure D(-) and L(+) enantiomers of lactic acid were prepared by fermentation reactions with specific bacteria. In addition, naturally deuterated ethanol was prepared and converted into diastereoisomers using mandelic acid. Various sugars and nutrients were fermented into lactic acid in water having different deuterium contents and ethanol samples were obtained from yeast fermentation of sugars from different botanical origins. The methine and methylene groups in lactic acid and ethanol respectively show similar deuterium contents which are related to that found in the fermentation water. However, the methyl groups of both molecules are significantly different whatever the botanical origin of the carbon source in the fermentation medium.

Production of L(+)-lactic acid from glucose and starch by immobilized cells of Rhizopus oryzae in a rotating fibrous bed bioreactor

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.

The effect of supplementation by different nitrogen sources on the production of lactic acid from date juice by Lactobacillus casei subsp. rhamnosus

Production of lactic acid from date juice by fermentation has been studied using Lactobacillus casei subsp. rhamnosus as the producer organism. The optimum substrate concentration, expressed in its glucose content, was 60 g l(-1). Various nitrogen sources were compared with yeast extract in terms of their efficiency for lactic acid production. None of these nitrogen sources gave lactic acid concentrations as high as that obtained with yeast extract. As yeast extract supplementation was not economically attractive, different proportions of (NH4)2SO4 and yeast extract were used. When the elemental nitrogen ratio of(NH4)2SO4 to yeast extract was 4:1, the substrate use and efficiency of lactic acid production were the same as in date juice supplemented with 20 g l(-1) yeast extract (0:5).

Comparative characterization of complete and truncated forms of Lactobacillus amylovorus alpha-amylase and role of the C-terminal direct repeats in raw-starch binding

Two constructs derived from the alpha-amylase gene (amyA) of Lactobacillus amylovorus were expressed in Lactobacillus plantarum, and their expression products were purified, characterized, and compared. These products correspond to the complete (AmyA) and truncated (AmyADelta) forms of alpha-amylase; AmyADelta lacks the 66-kDa carboxyl-terminal direct-repeating-unit region. AmyA and AmyADelta exhibit similar amylase activities towards a range of soluble substrates (amylose, amylopectin and alpha-cyclodextrin, and soluble starch). The specific activities of the enzymes towards soluble starch are similar, but the K(M) and V(max) values of AmyADelta were slightly higher than those of AmyA, whereas the thermal stability of AmyADelta was lower than that of AmyA. In contrast to AmyA, AmyADelta is unable to bind to beta-cyclodextrin and is only weakly active towards glycogen. More striking is the fact that AmyADelta cannot bind or hydrolyze raw starch, demonstrating that the carboxyl-terminal repeating-unit domain of AmyA is required for raw-starch binding activity.

Factors affecting the fermentative lactic acid production from renewable resources(1)

Parameters affecting the fermentative lactic acid (LA) production are summarized and discussed: microorganism, carbon- and nitrogen-source, fermentation mode, pH, and temperature. LA production is compared in terms of LA concentration, LA yield and LA productivity. Also by-product formation and LA isomery are discussed.

Production of lactic acid by Lactobacillus rhamnosus with vitamin-supplemented soybean hydrolysate

Batch fermentation studies were performed to evaluate the potentials of a complex nitrogen source, soybean, as an alternative to yeast extract for the economical production of lactic acid by Lactobacillus rhamnosus. An enzyme-hydrolysate of soybean meal, Soytone, with an adequate supplementation of vitamins was found to be highly effective in supporting lactic acid production from glucose and lactose. The effects of seven selected vitamins: d-biotin, pyridoxine, p-aminobenzoic acid, nicotinic acid, thiamine, pantothenic acid, and riboflavin, on cell growth and lactic acid production were investigated to provide the basis for the optimization of vitamin supplementation to minimize the cost. Pantothenic acid was the most required compound while the other six vitamins were also essential for high lactic acid productivity. As a result of the optimization, 15 g/l yeast extract could be successfully replaced with 19.3 g/l Soytone supplemented with the vitamins, resulting in a production of 125 g/l lactic acid from 150 g/l glucose. The volumetric productivity and lactate yield were 2.27 g/l/h and 92%, respectively, which were higher than those with 15 g/l yeast extract. The raw material cost was estimated to be 21.4 cent/kg lactic acid, which was only approximately 41% of that with yeast extract.

Production of multifunctional organic acids from renewable resources

Recently, the microbial production of multifunctional organic acid has received interest due to their increased use in the food industry and their potential as raw materials for the manufacture of biodegradable polymers. Certain species of microorganisms produce significant quantities of organic acids in high yields under specific cultivation conditions from biomass-derived carbohydrates. The accumulation of some acids, such as fumaric, malic and succinic acid, are believed to involve CO2-fixation which gives high yields of products. The application of special fermentation techniques and the methods for downstream processing of products are described. Techniques such as simultaneous fermentation and product recovery and downstream processing are likely to occupy an important role in the reduction of production costs. Finally, some aspects of process design and current industrial production processes are discussed.