The addition of pectinases and cellulases in the fermentation medium can enhance LA production . There is a great interest to introduce cellulosic and starchy materials as substrates for LA production due to their abundance, low price and for being derived from renewable sources . Coli strain could produce D-lactic acid from molasses . Molasses are waste products containing a large amount of sucrose and other essential nutrients, which can derive from sugar cane and sugar beet from sugar manufacturing plants.
3.1. Cheese whey
The number of downstream processing steps strongly influences the quality and the price of the product (Idler et al. 2015). Although the difference between the boiling point of lactic acid and water is relatively large, it is almost impossible to obtain pure crystalline lactic acid. If investment costs are high, the volumetric productivity is maximized by continuous operation (John et al.2007). If the substrate is expensive, the yield is maximized, by either batch or semicontinuous operation. The main sources of nitrogen are yeast extract and ammonium sulfate (Yin et al. 1997; Zhou et al. 1999; Jin et al. 2003).
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“Lactic acid recovery from whey ultrafiltrate fermentation broths and artificial solutions by nanofiltration,” Desalination228(1-3), 84-96. “Nanofiltration as key technology for the separation of LA and AA,” J. Membrane Sci. “Technological and economic potential of poly (lactic acid) and lactic acid derivatives,” FEMS Microbiol. “Use of lactate esters for improving the action of agricultural pesticides,” U. “Heterogeneous transformation of glycerol to lactic acid,” Top.
Raw material cost is one of the major factors in the economic production of lactic acid. However, waste products from food industries, agricultural industries, sugarcane mills, and biomasses can be used, which is advantageous from an environmental and economic standpoint. Several microorganisms and raw materials can be used in the production of lactic acid (Table 2). Lactic acid production by a chemical route is expensive and dependent on by-products from other industries, which are derived from fossil fuels (Datta and Henry 2006). They produced 40% (4,500 tons) of the lactic acid consumed in the USA (Trindade 2002).
Prospects for the Production of Lactic Acid
However, LAB species including Lactobacillus, Lactococcus, Leuconostoc, Streptococcus, and Pediococcus are also used as starter cultures in industrial food fermentations. LA is produced by glycolysis pathway under anaerobic conditions, and this compound can be produced from hexoses and pentoses LAB metabolism pathways, as indicated in Figure 1. Lactic acid bacteria (LAB) are gram-positive microorganisms known as the main safe industrial-scale producers of lactic acid (LA). Molasses, juices waste, starchy biomass, agricultural residues, and forestry residues that is rich in mono and disaccharides, which in some cases need to be hydrolysed by pectinases to enhance the LA production.
6.2. Chemical pretreatment
- Several studies have recently reported lactic acid production using whey (Tejayadi et al. 1995, Kim et al. 2006; Li et al. 2006).
- “Lactic acid recovery from cheese whey fermentation broth using combined ultrafiltration and nanofiltration membranes,” Appl.
- Global lactic acid demand was estimated to be 714.2 kilo tons in 2013, and it is expected to grow annually by 15.5% to reach 1,960.1 kilo tons by 2020 (Abdel-Rahman and Sonomoto 2016).
- The amount of copper (Cu-15; 15 μM/g, Cu-30; 30 μM/g and Cu-70; 70 μM/g) influence on the production of lactic acid (23.21 g/L), (17.44 g/L) and (16.53 g/L), respectively.
Neither pre-detoxification nor separation of fermentable sugars from lignin was needed before the fermentation. Bacillus also has metabolic capacity to produce LA. LAB possesses the aldolase enzyme and can convert glucose almost exclusively into LA. With improved tolerance to the acidified medium generated during fermentation. Moreover, chemical and physical pretreatment of substrates were explained. In this paper, different bacterial groups that capable of producing lactic acid at different rates and under different conditions were discussed.
The first company to produce lactic acid by chemical synthesis in significant amounts was Monsanto (Texas, USA) in 1963. Lactic acid production by chemical synthesis chicken road apk using the lactonitrile route, which was a by-product of acrylonitrile technology, was discovered in 1863 by Wislicenus (Benninga 1990). Overview of the two manufacturing methods of lactic acid, chemical synthesis and microbial fermentation (Wee et al. 2006) Although demand for PLA has expanded, its current production capacity of 450 million kg per year is dwarfed by the 200 billion kg of total plastics produced per year. New applications for lactic acid have been developed, such as the production of biodegradable and biocompatible PLA polymers (Abdel-Rahman et al. 2013), solvents, and oxygenated chemicals.
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- The manufacturer Archer Daniels Midland began using the fermentation process for lactic acid production in the early 1990s.
- Additionally, yeasts can tolerate environmental restrictions (for example acidic conditions), being the wild-type low lactic acid producers that have been improved by genetic manipulation.
- “Biotechnological routes based on lactic acid production from biomass,” Biotechnol.
- The batch fermentation process at a controlled pH significantly improves lactic acid production, yield, and productivity by different LAB strains, e.g., Lb.
In polymer applications, water is removed from lactic acid (CH3CHOHCOOH) in the presence of acid catalysts to form lactides (C6H8O4), as shown in Eq. It is also used in oral hygiene products (Castillo Martinez et al. 2013). In the pharmaceutical industry, lactic acid is used in implants, pills, dialysis, surgical sutures, and controlled drug release systems. It is an essential ingredient in fermented foods as well, like yogurt, butter, and canned vegetables.
Food waste contain a high amount of carbohydrate which causing it suitable as a substrate for lactic acid fermentation. Bailii has a high growth rate and biomass yield which could improve the fermentation processes of LA production. Zygosaccharomyces bailii has been suggested as another host for LA , due to its ability to tolerate environmental restrictions, including high sugar concentrations, acidic conditions, relatively high temperatures (higher than fermentation process) and LA production levels compared with S.
Vitaeruminis MTCC 5488 produced 38.5 g/l LA in fed-batch fermentation . WL-S20 generated L-lactic acid in fed-batch fermentation at pH 9.0, which would reduce a risk of the contamination during fermentation and also can produce lactic acid in thermal fermentation (≥50 °C) . High sulfuric acid consumption leads to form high content of insoluble calcium sulfate as gypsum compared to the amount of lactic acid produced, waste disposal concerns, further corrosion problems and a significant cost factor in the product recovery step of commercial operations. Glucose fermentation by homofermentative LAB needs somewhat acidic to neutral pH. However, low pH, has an inhibitory impact on cellular metabolism, in turn lactic acid production.
Cremoris produced LA at 6.34, 3.97 and 4.6 g l−1 h−1; with a yield of 0.98, 0.93 and 0.88 g/g lactose, respectively 13, 14, 182, 184. Semi-continuous fermentation conditions with nanofiltration membranes for recycling lactose and cells increased twice the LA production . On the other hand, continuous whey fermentation (without the requirement of high-volume) allowed obtaining a high LA productivity 13, 14, 180. For instance, whey supplemented with whey protein hydrolysate or yeast extract enhanced the LA production and decreased the unused nutrients loss during bioprocessing 178, 179. Lactose can be hydrolyzed into glucose and galactose by entering the cell via a permease and β-galactosidase (Figure 1) and can produce four LA moles 122, 177.
Lactic acid production to purification: A review
Organisms that produce the D(-)- or L(+)-isomer have two lactate dehydrogenase enzymes (LDH), which differ in their stereospecificity. Glycolysis only results in lactic acid as the end product of glucose metabolism. Homofermentative LAB convert glucose almost exclusively to lactic acid, while heterofermentative LAB catabolize glucose into ethanol, CO2, and lactic acid. LAB are unable to synthesize ATP by respiration, and their major end product from the energy-conserving fermentation of sugars is lactic acid.
In order to increase the LA productivity, ethanol production was stopped by the elimination of two pyruvate decarboxylase genes (PDC) 1 and 2, being these the primary enzymes contributing to ethanol production. This study was for the first time performed by Porro et al., 1995, having achieved an LA production of 20 g/l and productivity up to 11 g/L/h using engineered S. In transgenic strains, the coding section of pyruvate decarboxylase 1 (PDC1) was completely eliminated, and one or several copies of the d-lactate dehydrogenase (d-LDH) gene resources were inserted into the genome from mammalian LAB such as Leuconostoc mesenteroides subsp.
“Production of lactic acid from cheese whey by batch and repeated batch cultures of Lactobacillus sp. “Strain isolation and optimization of process parameters for bioconversion of glycerol to lactic acid,” J. “Extractive lactic acid fermentation with tri-n-decylamine as the extractant,” Enzyme Microb. “Recovery of lactic acid from sodium lactate by ion substitution using ion-exchange membrane,” Separ. “Batch production of L(+) lactic acid from whey by Lactobacillus casei (NRRL B-441),” J. Chem.
The pretreatment process is extremely crucial stage in lignocellulose bioconversion. Not only, this organised structure cause to prevent cellulose and hemicelluloses hydrolysis into fermentable sugars, but also inhibit the valorisation of lignin into chemicals. The chemical composition of substrate mainly consist of carbon and nitrogen compounds.
Many LAB produce only one isomer of lactic acid, but sometimes, depending on operating conditions, small amounts of both isomers can be produced. Another approach for production of lactic acid is from glycerol, which is a by-product of biodiesel production. Several studies have recently reported lactic acid production using whey (Tejayadi et al. 1995, Kim et al. 2006; Li et al. 2006). Lignocellulose biomass is also a promising source for lactic acid production because its represents the most abundant global source of biomass (Hama et al. 2015; Hu et al. 2015; Eom et al. 2015).
Lactic acid polymers have the advantage of being produced by renewable carbohydrates. Polymer production accounts for the largest portion of lactic acid demand (39%). In the cosmetic industry, lactic acid is used in the manufacture of hygiene and aesthetic products because of its moisturizing, antimicrobial, and rejuvenating effects on the skin. In the chemical industry, lactic acid can be converted to ethanol, propylene glycol, and acrylic polymers. In the food industry, which accounts for a large portion of the demand (35%), lactic acid has a number of uses. For applications in food and in medicine, L(+)-lactic acid is preferred because the metabolic conversion of L(+)-lactic acid in the body is faster than for D(-)-lactic acid.