Continuous Production Of Lactic Acid Research Articles

Multi-criteria analysis of cell-recycle based continuous lactic acid production process

ABSTRACT This study focuses on the optimization of the cell-recycle based continuous lactic acid (LA) fermentation production process with the estimation of improved kinetic parameters. The non-dominated sorting genetic algorithm II (NSGA-II) is used considering seven variables and five imposed constraints for multi-objective optimization (MOO) study. Three objectives namely LA productivity, substrate conversion, and yield are formed for the maximization purpose. Three different cases are constructed by using a combination of two bi-objectives and one tri-objective optimization problem, and the modified differential evolution (MDE) algorithm is used to individually optimize each case. Pareto ranking is carried out for MOO, and the best optimal solution is determined using the technique for order preference by similarity to the ideal solution (TOPSIS) method. The highest value of volumetric productivity of LA (184.363 kg/m3.h) is reported in case-4a. The highest yield (1.176) is reported in case-2, while the highest substrate conversion (0.963) is reported in case-1.

Continuous Production of Lactic Acid from Glycerol over Bifunctional Catalysts under Base-Free Conditions Using a Liquid-Phase Flow Reactor

Continuous Production of Lactic Acid from Glycerol over Bifunctional Catalysts under Base-Free Conditions Using a Liquid-Phase Flow Reactor

Evaluation of productive biofilms for continuous lactic acid production

In white biotechnology research, the putative superiority of productive biofilms to conventional biotransformation processes based on planktonic cultures has been increasingly discussed in recent years. In the present study, we chose lactic acid production as a model application to evaluate biofilm potential. A pureculture of Lactobacillus bacteria was grown in a tubular biofilm reactor. The biofilm system was cultivated monoseptically in a continuous mode for more than 3 weeks. The higher cell densities that could be obtained in the continuous biofilm system compared with the planktonic culture led to a significantly increased space-time yield. The productivity reached 80% of the maximum value 10 days after start-up and no subsequent decline was observed, confirming the suitability of the system for long-term fermentation. The analysis of biofilm performance revealed that productivity increases with the flow velocity. This is explained by the reduced retention time of the liquid phase in the reactor, and, thus, a minor pH drop caused by the released lactic acid. At low flow velocities, the pH drops to a value where growth and production are significantly inhibited. The biofilm was visualized by magnetic resonance imaging to analyze biofilm thickness. To deepen the understanding of the biofilm system, we used a simple model for cell growth and lactic acid production.

Techno-economic assessment of non-sterile batch and continuous production of lactic acid from food waste

Non-sterile lactic acid (LA) fermentation of highly viscous food waste was demonstrated in batch and continuous flow fermentations. With Streptococcus sp., an indigenous consortium, and/or applied glucoamylase, food waste was fermented without addition of external carbon or nitrogen sources. Experimental results were used for economic and energy evaluations under consideration of different catchment area sizes from 50,000 to 1,000,000 inhabitants. During batch mode, addition of glucoamylase resulted in a titer (after 24 h), yield, and productivity of 50 g L−1, 63%, and 2.93 g L−1h−1, respectively. While titer and yield were enhanced, productivity was lower during continuous operation and 69 g L−1, 86%, and 1.27 g L−1h−1 were obtained at a dilution rate of 0.44 d−1 when glucoamylase was added. Both batch and continuous flow fermentations were found economically profitable with food waste from 200,000 or more inhabitants.

A review on the current developments in continuous lactic acid fermentations and case studies utilising inexpensive raw materials

Abstract The numerous applications of lactic acid have made it one of the most important platform chemicals and, for many years, its biotechnological production has been the topic of intensive research. Currently, most of the lactic acid is manufactured in batch mode; however, continuous mode could offer various advantages, especially in terms of productivity. This review provides a summary of the most recent studies on continuous lactic acid production. Potential advantages of continuous over batch mode, the improvements that high cell densities can represent, utilisation of low cost substrates and some economic aspects of continuous mode are discussed. The review is complemented by 3 experimental case studies utilising inexpensive substrates: tapioca starch hydrolysate, molasses combined with rapeseed meal hydrolysate and acid whey. In all cases, continuous cultivation was coupled with cell recycling using hollow-fibre membranes for l - or d -lactic acid production. Lactic acid productivities higher than 5 g l−1 h−1 and substrate conversion yields above 80% were achieved for all the cases. Final lactic acid concentrations were 50.3, 59.6 and 45.9 g l−1 for the tapioca starch hydrolysate, molasses and acid whey respectively. These results support the claim that continuous cultivation using cell recycling is a promising approach for high lactic acid productivities.

Thin film composite nanofiltration membrane for lactic acid production in membrane bioreactor

In this work the thin film composite nanofiltration (TFC-NF) membrane was fabricated for lactic acid separation in membrane bioreactor. The morphological study was carried out with scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM and AFM studies indicated that using interfacial polymerization causes a rough and dense film to be formed on the polyethersulfone (PES) support membrane. The permeate flux and separation properties of the membrane was investigated at 25 °C and trans membrane pressure (TMP) of 5 bar and was compared with 3 commercial NF membranes. The high lactose and low lactic acid rejection of 80% and 19% was obtained with TFC NF membrane. The membrane was used to produce lactic acid from whey lactose in membrane bioreactor (MBR). Continuous lactic acid production has two stages of Integration of fermentation and membrane separation which were assessed and compared to the conventional bioreactor performance (CBR). In order to produce lactic acid from whey, the Lactobacillus bulgaricus (ATCC 8001) was used in the process. The maximal productivity of 6.1 gL−1 h−1 was obtained at the dilution rate of 0.24 h−1, while the value obtained in the CBR was 3.4 gL−1 h−1 at the same dilution rate. The maximum concentration of lactic acid was obtained at the dilution rate of 0.04 h−1 in both MBR and CBR with values of 38.2 and 22.5 gL−1.

Continuous Production of Lactic Acid in a Two Stage Process Using Immobilized Lactobacillus casei MTCC 1423 Cells

Continuous Production of Lactic Acid in a Two Stage Process Using Immobilized Lactobacillus casei MTCC 1423 Cells

Investigation of spiral-wound membrane modules for the cross-flow nanofiltration of fermentation broth obtained from a pilot plant fermentation reactor for the continuous production of lactic acid

BackgroundThe separation performance of seven polymer membranes for the nanofiltration of sodium lactate in fermentation broth was investigated. Each module was introduced into the test stand, and the system curve was obtained by recording the permeate flow velocity at different pump head levels. Performance benchmarks were good permeate quality, as determined by high permeate flow velocity, high sodium lactic concentration, low ion impurity concentration, and low organic impurity concentration. Market research has shown that three companies, DOW (TW30, SW30, NF45), General Electric (DK73, DL73), and Microdyn-Nadir (NP30), distributed spiral-wound membrane modules for cross-flow filtration in a 2.5 by 40-in. module size, suitable for operation in the filtration test stand.ResultsThe measured permeate flow velocity was found to vary widely between the membranes. At a pump head of 250 m, DK73, NP30, and DL73 generated more than 200, 300, and 400% higher permeate flow velocities, respectively, than TW30 and NF45. A key benchmark, lactate rejection, was also highly dependent upon membrane type. The NP30, NF45, and TW30 membranes showed a decrease in lactate permeate flow velocity of 117, 83, and 348% starting at 205, 250, and 300 m, respectively.ConclusionsThe DL73 had the overall best performance according to the measured fermentation broth and lactic acid permeability. The presented method for the graphical analysis of the membrane performance proofed to be a useful tool for the filtration engineer.

Continuous production of lactic acid from glycerol in alkaline medium using supported copper catalysts

With increasing demand for biodiesel, large quantity of crude glycerol has been produced both in Brazilian and world market, and this excess glycerol has become a problem that must be solved. Several studies have been performed with the objective to transform glycerol in value-added chemical products. Lactic acid has wide uses in chemical and food industries, and the hydrothermal transformation of glycerol to lactic acid is presented as an alternative to conventional production process. In this study, the production of lactic acid from glycerol under alkaline conditions, using copper (20wt.% CuO) catalysts supported on Al2O3, ZnO and MgO in continuous flow reaction system was investigated. The catalysts were prepared by impregnation method and characterized by XRF, XRD, N2 adsorption–desorption, TPR, and TPD-CO2 and the dispersion of copper was determined by N2O oxidation. The reaction was carried out at 240°C, 35atm, with space velocity (WHSV) of 2h−1, 10vol.% glycerol solution and NaOH/glycerol molar ratio of 0.5, 0.75 and 1.0. All catalysts showed high conversion of glycerol with yield and selectivity to lactic acid in the range of 80 and 90%, respectively, when the reactions are performed with NaOH/glycerol molar ratio of 1.0.

Modeling the continuous lactic acid production process from wheat flour.

A kinetic model of the simultaneous saccharification, protein hydrolysis, and fermentation (SSPHF) process for lactic acid production from wheat flour has been developed. The model describes the bacterial growth, substrate consumption, lactic acid production, and maltose hydrolysis. The model was fitted and validated with data from SSPHF experiments obtained under different dilution rates. The results of the model are in good agreement with the experimental data. Steady state concentrations of biomass, lactic acid, glucose, and maltose as function of the dilution rate were predicted by the model. This steady state analysis is further useful to determine the operating conditions that maximize lactic acid productivity.

Improving the lactic acid production of Actinobacillus succinogenes by using a novel fermentation and separation integration system

This work describes the development of a novel integrated system for lactic acid production by Actinobacillus succinogenes. Fermentation and separation were integrated with the use of a microfiltration (MF) membrane, and lactic acid was recovered by resin adsorption following MF. The fermentation broth containing residual sugar and nutrients was then recycled back into the fermenter after lactic acid adsorption. This novel approach overcame the problem of product inhibition and extended the cell growth period from 41h to 120h. Production of lactic acid was improved by 23% to 183.4gL−1. The overall yield and productivity for glucose were 0.97gg−1 and 1.53gL−1h−1, respectively. These experimental results indicate that the integrated system could benefit continuous production of lactic acid at high levels.

Modeling and multi-criteria optimization of an industrial process for continuous lactic acid production

The key feature of this paper is the optimization of an industrial process for continuous production of lactic acid. For this, a two-stage fermentor process integrated with cell recycling has been mathematically modeled and optimized for overall productivity, conversion, and yield simultaneously. Non-dominated sorting genetic algorithm (NSGA-II) was applied to solve the constrained multi-objective optimization problem as it is capable of finding multiple Pareto-optimal solutions in a single run, thereby avoiding the need to use a single-objective optimization several times. Compared with traditional methods, NSGA-II could find most of the solutions in the true Pareto-front and its simulation is also very direct and convenient. The effects of operating variables on the optimal solutions are discussed in detail. It was observed that we can make higher profit with an acceptable compromise in a two-stage system with greater efficiency.

Direct production of l (+) lactic acid in a continuous and fully membrane-integrated hybrid reactor system under non-neutralizing conditions

Experimental investigations were carried out on continuous and direct production of l (+) lactic acid by fermentation of sugarcane juice in a novel two stage membrane-integrated fermentor under non-neutralizing conditions. Novelty of the integrated system lies in high degree of purity, yield and productivity of lactic acid from a relatively cheap and renewable carbon source in a very compact, flexible yet eco-friendly plant. Integration of cross flow microfiltration and nanofiltration membrane modules in two stages with the fermentor helped achieve reasonably high purity, productivity and yield by continuous recycling of cells and unconverted sugars. The system could be operated at steady state for a constant fermentor capacity and also at different set flux values ranging from 63 l m −2 h −1 to 76 l m −2 h −1. Cross flow microfiltration membrane modules ensured almost complete separation and recycle of cells without much fouling problem whereas composite nanofiltration membrane module helped achieve 96% recovery and recycle of unconverted sugars along with high degree of purity. When operated at a dilution rate of 0.15 h −1, the yield and volumetric productivity of l (+) lactic acid were 0.96 g g −1 and 12.40 g l −1 h −1 respectively. Volumetric productivity could be increased further to 13.4 g l −1 h −1 with increase of dilution rate to 0.18 h −1. Flat sheet cross flow modular design permitted continuous production of lactic acid in a highly flexible, largely fouling-free and environmentally benign plant as direct lactic acid was obtained instead of lactate salts of a conventional process.

Lactic acid production by Lactobacillus delbrueckii in a dual reactor system using packed bed biofilm reactor

An integrated dual reactor system for continuous production of lactic acid by Lactobacillus delbrueckii using biofilms developed on reticulated polyurethane foam (PUF) is demonstrated. Lactobacillus delbrueckii was immobilized on PUF, packed in a bioreactor and used in lactic acid fermentation. The rate of lactic acid production was significantly high with a volumetric productivity of 5 g l(-1) h(-1) over extended period of time. When coupled to a bioreactor, the system could be operated as dual reactor for over 1000 h continuously without augmentation of inoculum and no compromise on productivity. Polyurethane foams offer an excellent support for biofilm formation. The system was very robust and could be operated for prolonged period at a volumetric productivity of 4-6 g l(-1) h(-1).

Revalorization of hemicellulosic trimming vine shoots hydrolyzates trough continuous production of lactic acid and biosurfactants by L. pentosus

This work proposes the utilization of trimming vine shoots hydrolyzates by Lactobacillus pentosus for lactic acid employing continuous culture and the evaluation of biosurfactants production. The treatment of hydrolyzates with sulphuric acid (prehydrolysis) allowed the solubilization of hemicelluloses to give liquors containing 18 g/L of xylose, 11.1 g/L of glucose, 4.3 g/L of arabinose and 4 g/L of acetic acid. Continuous fermentation of hemicellulosic hydrolyzates gave a Q P = 3.10 g of lactic acid/L h and Y P/S = 0.70 g of lactic acid/g of sugars for a dilution rate of 0.02 h −1 using 10 g/L of corn steep liquor and 10 g/L of yeast extract as nutrients. When nutrients were replaced by 20 g/L of distilled lees from white wine production the same results were obtained without interfering, lees, in the lactic acid recovery from the fermentation medium. On the other hand, L. pentosus cells were submitted to extraction process with PBS to evaluate the intracellular biosurfactants. In presence of vinification lees or corn steep liquid plus yeast extract, the extracted biosurfactants of L. pentosus reduced the superficial tension of PBS in 23.5 and 25.5 m N/m, respectively. No extracellular biosurfactants were observed.

Continuous lactic acid production in whey permeate/yeast extract medium with immobilized Lactobacillus helveticus in a two-stage process: Model and experiments

The effects of different culture parameters and operating strategies were tested on lactic acid production from whey permeate/yeast extract medium by immobilized Lactobacillus helveticus in a continuous two-stage process. High lactic acid productivities of 19–22 g l −1 h −1 and low residual sugar was achieved with an overall dilution rate of 0.5 h −1 and 10 g l −1 yeast extract. Lowering the yeast extract concentration from 10 to 1 g l −1 resulted in a gradual loss of activity with time in both reactors, leading to an overall lactic acid productivity of 10.5 g l −1 h −1 with 24 g l −1 residual sugar after 47 h. Inversion of the first and second reactor in the two-stage process led to an important drop in productivity which was only partly restored in the next 3 days of culture. Lactic acid and residual sugar concentrations in both reactors were predicted by a mathematical model, which combined mass transfer equations with a free-cell kinetic model of Lb. helveticus and did not use any fitting factor. Predicted concentrations were close to measured values during the first 18–24 h batch or continuous culture and, in general, during pseudo-steady-state continuous cultures in both reactors after this initial colonization period. However, transitions to a new pseudo-steady state, after changes in dilution rate and/or yeast extract concentration, were much slower in the experiment than those predicted by the model. Biomass and pH-gradients within gel beads, measured with fluorescent dyes and microelectrode, respectively, were only qualitatively predicted by the model. Our data suggest that an accurate description of immobilized cell activities cannot be done with kinetic models for free cells, especially for long-culture times, due to a change in the physiology of immobilized cells.

Comparison of Lactic Acid Productivities at High Substrate Conversions in a Continuous Two-stage Fermenter With Cell Recycle Using Different Kinetic Models

The steady-state performance of a two-stage recycle fermenter with two different types (I and II) of configurations for staging was investigated numerically for the continuous production of lactic acid. In Type I the bleed broth withdrawn from the first stage is supplied to the second fermenter, and in Type II both filtrate and bleed broth from the first stage are introduced to the second stage. Using four different kinetic models taken from the literature, the effects of operating parameters on the overall lactic acid productivities and the overall substrate conversions are examined. At moderate conversions, productivities for Type I operation are found to be higher than those for Type II and for the single-stage system. In the case of high conversions close to complete consumption, Type II operation is more efficient than the Type I and single-stage systems. For 99% conversion and 40 kg m−3 substrate feed concentration, productivities for Type II are predicted to be 14–74% higher compared to those for the single-stage system at the same bleed ratios.

Continuous cultivation ofLactobacillus rhamnosus with cell recycling using an acoustic cell settler

Continuous production of lactic acid from glucose by Lactobacillus rhamnosus with cell recycling using an acoustic cell settler was carried out. The performance of the system, such as the concentration of cell and product were compared with the control experiment without recycling. The acoustic settler showed cell separation efficiency of 67 during the continuous operation and the cell concentration in the fermentor with recycle exceeded that of the control by 29. Com- pared with the control, lactic acid production was increased by 40, while glucose consumption was only increased by 8. The higher value of lactic acid production to substrate consumption (Y P/S , product yield coefficient) achieved by cell recycling is interpreted to indicate that the recy- cled cell mass consumes less substrate to produce the same amount of product than the control. Within system environmental changes due to the longer mean cell residence time induced the cells maintaining the metabolic pathways to produce less by-product but more product, lactic acid.

A continuous lactic acid production system using an immobilized packed bed of Lactobacillus helveticus

A 5 l packed bed bioreactor was used to study the effect of initial lactose concentration and hydraulic retention time (HRT) on cell growth, lactose utilization and lactic acid production. Up to 95% of the initial lactose concentration was utilized at longer HRTs (30-36 h). The study showed that lactic acid production increased with increases in HRT (12-36 h) and initial lactose concentrations. The highest lactic acid production rate (3.90 g l(-1) h(-1)) was obtained with an initial lactose concentration of 100 g/l and an HRT of 18 h, whereas the lowest lactic acid production rate (1.35 g l(-1) h(-1)) was obtained with an initial lactose concentration of 50 g/l and an HRT of 36 h. This suggested that optimal lactic acid production can be achieved at an HRT of 18 h and initial lactose concentration of 100 g/l.

Continuous lactic acid fermentation using a plastic composite support biofilm reactor.

An immobilized-cell biofilm reactor was used for the continuous production of lactic acid by Lactobacillus casei subsp. rhamnosus (ATCC 11443). At Iowa State University, a unique plastic composite support (PCS) that stimulates biofilm formation has been developed. The optimized PCS blend for Lactobacillus contains 50% (wt/wt) agricultural products [35% (wt/wt) ground soy hulls, 5% (wt/wt) soy flour, 5% (wt/wt) yeast extract, 5% (wt/wt) dried bovine albumin, and mineral salts] and 50% (wt/wt) polypropylene (PP) produced by high-temperature extrusion. The PCS tubes have a wall thickness of 3.5 mm, outer diameter of 10.5 mm, and were cut into 10-cm lengths. Six PCS tubes, three rows of two parallel tubes, were bound in a grid fashion to the agitator shaft of a 1.2-1 vessel for a New Brunswick Bioflo 3000 fermentor. PCS stimulates biofilm formation, supplies nutrients to attached and suspended cells, and increases lactic acid production. Biofilm thickness on the PCS tubes was controlled by the agitation speed. The PCS biofilm reactor and PP control reactor achieved optimal average production rates of 9.0 and 5.8 g l(-1) h(-1), respectively, at 0.4 h(-1) dilution rate and 125-rpm agitation with yields of approximately 70%.