Production of lactic acid from beet molasses by calcium alginate immobilized Lactobacillus delbrueckii IFO 3202

Lactic acid was produced from pretreated beet molasses by the homofermentative organism Lactobacillus delbrueckii subsp delbrueckii IFO 3202 entrapped in calcium alginate gel using batch, repeated batch and continuous fermentation systems. In batch fermentation studies successful results were obtained with 2.0–2.4 mm diameter beads prepared from 2% sodium alginate solution. The highest effective yield (82.0%) and conversion yield (90.0%) were obtained from substrate concentrations of 52.1 and 78.2 g dm⁻³ respectively. The gel beads produced lactic acid for 14 consecutive batch fermentations without marked activity loss and deformation. In the continuous fermentation, the highest lactic acid (4.22%) was obtained at a dilution rate of 0.1 h⁻¹ while the highest productivity (13.92 g dm⁻³ h⁻¹) was obtained at a dilution rate of 0.4 h⁻¹. © 1999 Society of Chemical Industry     

Batch production of L(+) lactic acid from whey by Lactobacillus casei (NRRL B‐441)

The effects of temperature, pH, and medium composition on lactic acid production by Lactobacillus casei were investigated. The highest lactic acid productivity values were obtained at 37 °C and pH 5.5. The productivity was 1.87 g dm^?3 h^?1 at 37 °C in shake flasks. In the fermenter, a productivity of 3.97 g dm^?3 h^?1 was obtained at pH 5.5. The most appropriate yeast extract concentration was 5.0 g dm^?3. Whey yielded a higher productivity value than the analytical lactose and glucose. Initial whey lactose concentration did not affect lactic acid productivity. MnSO₄ ·H₂O was necessary for lactic acid production by L casei from whey. Product yields were approximately 0.93 g lactic acid g lactose^?1. Copyright © 2004 Society of Chemical Industry     

Cell recycle and broth reuse fermentation with cross-flow filtration and ion-exchange resin

A novel integrated fermentation system in which cross-flow filtration was coupled to an anion-exchange resin column was developed to achieve biomass recycle and broth reuse for lactic acid fermentation. An anion-exchange resin column was employed to recover lactic acid from the spent broth. The effluent was diluted with fresh medium, supplemented with glucose and nutrients. Spent broth was reused for three consecutive biomass recycle fermentations with no significant decrease in fermentation performance. The fermentation system enabled simultaneously high productivity of lactic acid (average value 7·75 g dm⁻³ h⁻¹ and total amount of lactic acid produced 85·21 g dm⁻³ after 11 h fermentation), high productivity of cells (average value 2·00 g dm⁻³ h⁻¹) and efficient utilization of medium (about 75% of the spent broth was reutilized). The system described may be applied to other organic fermentations subject to end-product inhibition.     

Continuous ethanol production from carob pod extract by immobilized Saccharomyces cerevisiae in a packed-bed reactor

The continuous production of ethanol from carob pod extract by immobilized Saccharomyces cerevisiae in a packed-bed reactor has been investigated. At a substrate concentration of 150 g dm^?3, maximum ethanol productivity of 16 g dm^?3 h^?1 was obtained at D = 0·4 h^?1 with 62·3% of theoretical yield and 83·6% sugars′ utilization. At a dilution rate of 0·1 h^?1, optimal ethanol productivity was achieved in the pH range 3·5–5·5, temperature range 30–35·C and initial sugar concentration of 200 g dm^?3. Maximum ethanol productivity of 24·5 g dm^?3 h^?1 was obtained at D = 0·5 h^?1 with 58·8% of theoretical yield and 85% sugars′ utilization when non-sterilized carob pod extract containing 200 g dm^?3 total sugars was used as feed material. The bioreactor system was operated at a constant dilution rate of 0·5 h^?1 for 30 days without loss of the original immobilized yeast activity. In this case, the average ethanol productivity, ethanol yield (% of theoretical) and sugars′ utilization were 25 g dm^?3 h^?1, 58·8% and 85·5%, respectively.     

Technological and kinetic aspects of sublethal acid toxicity in microbial gum production

Chemostat culture of Xanthomonas campestris were obtained at a dilution rate of 0·05 h⁻¹ and the normal feed then supplemented with 0·58 and 1·74 mmol dm⁻³ isobutyric acid (IBA). Data revealed that the organism responded to sublethal acid stress by overproducing xanthan. The acid additions led to transient zones in the continuous cultivation profiles. By adding feed containing 1·74 mmol dm⁻³ IBA, volumetric growth rate immediately decreased from 0·059 to 0·026 g dm⁻³ h⁻¹ whereas the specific xanthan formation rate increased from 0·23 g g⁻¹ biomass h⁻¹ to a maximum 0·65 g g⁻¹ biomass h⁻¹ (with 1·0 mmol dm⁻³ IBA addition), before decreasing as the concentration of acid attained that of the feed. By monitoring the outlet CO₂ in parallel with biomass and polysaccharide levels in the IBA fermentation a 10% diversion of the total carbon flux from biomass synthesis to xanthan biosynthesis was detected. A consistent pattern of variation in activity was detected in enzymes of intermediary metabolism, suggesting an action at the regulatory level. Enhanced activities of carbon catabolism and xanthan anabolic reactions (phosphomannose isomerase) were observed in the presence of the acid. Batch experiments carried out in the pres-ence of IBA gave results which correlated with the undissociated acid form con-centration. An undissociated acid fraction of 6·5×10⁻³ mmol dm⁻³ was calculated in a set of flasks under the same conditions and a statistically vali-dated 12% increase in xanthan production was found. The maximum activation was determined to be below 1·1×10⁻² mmol dm⁻³ when a 58% specific xanthan production rate increase occurred in parallel with a 35% decrease in biomass concentration.     

Fermentative production of L(+)‐lactic acid from starch hydrolyzate and corn steep liquor as inexpensive nutrients by batch culture of Enterococcus faecalis RKY1

BACKGROUND: Attempts were made to determine the lactic acid production efficiency of novel isolate, Enterococcus faecalis RKY1 using four different starches (corn, tapioca, potato, and wheat starch) with different concentrations (50, 75, 100, and 125 g L^?1) and corn steep liquor as an inexpensive nitrogen source. RESULTS: The yield of lactic acid from each starch was higher than 95% based on initial starch concentrations. High lactic acid concentration (129.9 g L^?1) and yield (1.04 g‐lactic acid g^?1‐starch) were achieved faster (84 h) from 125 g L^?1 of corn starch. Among the starches used, tapioca starch fermentation usually completed in a shorter incubation period. The final dry cell weight was highest (7.0 g L^?1) for the medium containing 75 g L^?1 of corn starch, which resulted in maximum volumetric productivity of lactic acid (3.6 g L^?1 h^?1). The addition of 30 g L^?1 corn steep liquor supplemented with a minimal amount of yeast extract supported both cell growth and lactic acid fermentation. CONCLUSION: Enterococcus faecalis RKY1 was found to be capable of growing well on inexpensive nutrients and producing maximum lactic acid from starches and corn steep liquor as lower‐cost raw materials than conventionally‐used refined sugars such as glucose, and yeast extract as an organic nitrogen source in laboratory‐scale studies. These fermentation characteristics are prerequisites for the industrial scale production of lactic acid. Copyright © 2008 Society of Chemical Industry     

Effect of zeolite addition on ethanol production from glucose by Saccharomyces bayanus

Zeolite NaY at 5 g dm⁻³ concentration, was selected to improve the production of ethanol fermentation by Saccharomyces bayanus from high glucose concentration media. The highest ethanol productivity (3·07 g dm⁻³ h⁻¹) was obtained from a 220 g dm⁻³ initial glucose concentration, while the highest ethanol concentration (130 g dm⁻³) was obtained from a 350 g dm⁻³ glucose medium. The zeolite is believed to have acted as a pH regulator, maintaining the pH value around 3·7–3·8. Under these conditions cellular viability was preserved and metabolic activity was maintained. Thus all the glucose was consumed, and high ethanol productivity and concentration were obtained. Therefore, the addition of zeolite improved ethanol production from high concentrations of glucose by Saccharomyces bayanus. © 1998 Society of Chemical Industry     

D‐Lactic acid production from waste cardboard

The effects caused by alkaline treatment on the susceptibility of waste cardboard to enzymatic hydrolysis have been studied. Optimised conditions leading to extensive saccharification of both cellulose (870 g kg^?1 conversion) and hemicelluloses (845 g kg^?1 conversion) were identified. Samples treated under selected operational conditions were employed for producing D ‐lactic acid by simultaneous saccharification and fermentation (SSF) in media containing cellulases, β‐glucosidase and Lactobacillus coryniformis ssp torquens cells. SSF fed‐batch experiments led to D ‐lactic acid concentrations up to 23.4 g dm^?3 at a product yield of 514 g lactic acid kg^?1 of potential glucose and a volumetric productivity of 0.48 g dm^?3 h^?1. Copyright © 2004 Society of Chemical Industry     

Kinetics of Lactic Acid Fermentation by Lactobacillus delbrueckii Grown on Beet Molasses

The fermentation kinetics for the conversion of beet molasses, a valuable and economical fermentation substrate, to lactic acid by the homofermentative organism Lactobacillus delbrueckii C.E.C.T. 286 have been studied at controlled pH and temperature under anaerobic batch conditions. An inhibitory effect of lactic acid on fermentation of beet molasses has been found. The bacterium was able to produce lactic acid even after growth ceased. A kinetic model for the fermentation is proposed. From this model, the maximum allowable lactic acid concentration above which growth stops and the lactic acid level above which bacteria stop producing lactic acid were found to be 45 g dm⁻³ and 57 g dm⁻³, respectively. © 1997 SCI.     

Continuous process for yeast biomass production from sugar beet stillage by a novel strain of Candida rugosa and protein profile of the yeast

Thermotolerant yeast Candida rugosa isolated from East Africa was used for the continuous production of yeast protein from sugar beet stillages at 40°C. At a dilution rate of 0·15 h⁻¹, biomass productivity was at a maximum (0·85 dm⁻³ h⁻¹) and the Chemical Oxygen Demand reduction rate of the stillage was 30·4%. This yeast contained 45·1% crude protein, 36·5% actual protein and 5·6% RNA. The yeast protein had adequate essential amino acids, except for sulphur-containing types.     

Effect of inorganic phosphate on lactate production by Lactobacillus helveticus grown on supplemented whey permeate

For batch culture of lactic acid bacteria, seed cultures have to be highly supplemented with complex substrates to obtain an active inoculum. In contrast, for industrial applications, nitrogen supplementation of the fermenter culture must be kept low to minimize costs. Addition of inorganic phosphate, a low cost component, to the medium increased the lactic acid production rate (40% for media supplemented with 2 g dm⁻³ yeast extract), but had no effect on growth rate. This effect was absent for high‐nitrogen supplemented medium (20 g dm⁻³ yeast extract), because of the lack of phosphorus limitation. © 2000 Society of Chemical Industry     

Experimentation of a new mode of batch culture for lactic acid bacteria: cell reuse with an initial period of cell reactivation at acidic pH

Cell reuse was compared with conventional batch culture for lactic acid fermentation, the objective was to simplify the batch process and to alleviate the need for added nitrogen. At high levels of nitrogen supplementation to the culture medium (20 g dm^?3 yeast extract and 5 g dm^?3 each of tryptic and pancreatic casein peptones), similar mean production rates were obtained with partial cell reuse and the conventional batch process, without any additional gain when cells were initially reactivated at acidic pH. On the other hand, cell reuse with an initial period without pH control appeared particularly effective for low levels of nitrogen supplementation (5 g dm^?3 yeast extract): a 57% increase in the mean production rate with regard to the conventional batch process was obtained. © 2001 Society of Chemical Industry     

Effect of Saccharomyces cerevisiae fermentation conditions on expanded bed adsorption of heterologous cutinase

The effect of culture media composition, and fermentation conditions and strategy on the growth and cutinase production of recombinant Saccharomyces cerevisiae and subsequent cutinase purification by expanded bed adsorption (EBA) was studied. The reduction in the amount of yeast extract used as nitrogen source from 20 g dm^?3 to 10 g dm^?3 in batch cultures led to a 29% decrease in the heterologous cutinase production, while the 5% cutinase dynamic adsorption capacity (q5%) on the cation Streamline SP XL was increased 6.7‐fold. By dilution of the whole fermentation broth, performed with the lowest yeast extract content, which reduces conductivity, the q5% was additionally increased by 1.9‐fold. After implementation of a fed‐batch strategy the cutinase concentration, cutinase yield on carbon source, cutinase yield on nitrogen source and productivity were increased by 10.8‐, 2.9‐, 5.3‐ and 6.4‐fold, respectively, in relation to the previously‐mentioned batch fermentation. However, the increased cutinase production was compromised by heterologous protein loss during the EBA recovery operation and the cutinase dynamic adsorption capacity and purification productivity decreased by 90% and 75%, respectively. Thus, target protein production by S cerevisiae fermentation and a downstream process with EBA cannot be considered as separate entities, where the understanding of the factors that affect the interactions among them are crucial towards optimization of the overall production process of heterologous proteins. © 2002 Society of Chemical Industry     

Optimization of lactic acid production from whey by L casei NRRL B‐441 immobilized in chitosan stabilized Ca‐alginate beads

The production of lactic acid from whey by Lactobacillus casei NRRL B‐441 immobilized in chitosan‐stabilized Ca‐alginate beads was investigated. Higher lactic acid production and lower cell leakage were observed with alginate–chitosan beads compared with Ca‐alginate beads. The highest lactic acid concentration (131.2 g dm^?3) was obtained with cells entrapped in 1.3–1.7 mm alginate–chitosan beads prepared from 2% (w/v) Na‐alginate. The gel beads produced lactic acid for five consecutive batch fermentations without marked activity loss and deformation. Response surface methodology was used to investigate the effects of three fermentation parameters (initial sugar, yeast extract and calcium carbonate concentrations) on the concentration of lactic acid. Results of the statistical analysis showed that the fit of the model was good in all cases. Initial sugar, yeast extract and calcium carbonate concentrations had a strong linear effect on lactic acid production. The maximum lactic acid concentration of 136.3 g dm^?3 was obtained at the optimum concentrations of process variables (initial sugar 147.35 g dm^?3, yeast extract 28.81 g dm^?3, CaCO₃ 97.55 g dm^?3). These values were obtained by fitting of the experimental data to the model equation. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in lactic acid production using alginate–chitosan‐immobilized cells. Copyright © 2005 Society of Chemical Industry     

Use of sweet sorghum juice for lactic acid fermentation: preliminary steps in a process optimization

BACKGROUND: Lactic acid has many applications in the chemical industries and it can be produced economically by microorganisms using biomass raw materials of different origins. Sweet sorghum juice is a high sugar content raw material with potential for lactic acid production because after hydrolysis of its sucrose content the remaining glucose and fructose can supply the carbon demand of most lactic acid bacteria. However, satisfying the nitrogen and B‐vitamin needs of the bacteria by supplementation with yeast extract and/or other alternative nitrogen‐containing supplements can make the process too expensive. RESULTS: Using a statistical optimization process much of the yeast extract can be replaced by a cheaper alternative nitrogen source, namely wheat gluten. This resulted in a fermentation with 99% lactic acid yield and 3.04 g L^?1 h^?1 volumetric productivity. CONCLUSION: Using response surface methodology (RSM) media optimization was performed for lactic acid fermentation with an industrially acceptable result, reducing the costs of raw materials by half, replacing yeast extract by an alternative nitrogen source and applying yeast extract only as a source of micro‐elements (vitamins, salts, etc.) Copyright © 2010 Society of Chemical Industry     

Strategies to improve the bioconversion of processed wood into lactic acid by simultaneous saccharification and fermentation

In the one‐step conversion of wood into lactic acid by Simultaneous Saccharification and Fermentation (SSF), inhibition effects caused by hydrolysis‐ and fermentation‐derived compounds on both enzymatic activity and fermentative ability of microorganisms appear when the operation is carried out under conditions leading to high productivities. The main effects inhibiting SSF have been assessed, and the results obtained in fed‐batch experiments allowed the definition of strategies for improving the overall bioconversion process. As cellobiose caused significant inhibition of cellulases, the supplementation of media with β‐glucosidase resulted in improved kinetics and yields. The inhibition of both enzymatic activity and microbial metabolism by lactic acid was confirmed. Intermittent removal of lactic acid by passing the fermentation media through an anion‐exchange resin column resulted in increased productivities and yields. Improved conversion of pretreated wood into lactic acid (67% conversion of cellulose into lactic acid, with maximum lactic acid concentration of 108 g dm^?3 and a productivity of 0.94 g dm^?3 h^?1) was achieved combining multiple substrate addition, supplementation with fresh nutrients and enzymes and removal of lactic acid. © 2001 Society of Chemical Industry     

Mathematical modelling of the alcoholic fermentation of glucose by Zymomonas mobilis mobilis

The kinetics of alcoholic fermentation of a strain of Zymomonas mobilis, isolated from sugarcane juice, has been studied with the objective of determining the constansts of a non-structured mathematical model that represents the fermentation process. Assays in batch and in continuous culture have been carried out with different initial concentrations of glucose. The final concentrations of glucose, ethanol and biomass were determined. The following kinetic parameters were obtained: μ_max, 0·5 h^?1; K_s, 4·64 g dm^?3; P_max, 106 g dm^?3; Y_x/s, 0·0265 g g^?1; m, 1·4 g g^?1 h^?1; α, 17·38 g g^?1; β, 0·69 g g^?1 h^?1.     

Novel repeated batch operation for flash fermentation system: Experimental data and mathematical modelling

A novel repeated batch operation mode was proposed for ethanol fermentation, where the fermenter beer was periodically exchanged between the fermenter with biomass recycle and the distillation unit, to promote the selective removal of ethanol. Using the mathematical model developed, as based on the experimental results, the optimal operation of the proposed method was shown to attain high performance, with a productivity of about 12 g dm⁻³ h⁻¹ and a product concentration of 400 g dm⁻³.     

Continuous ethanol fermentation using immobilized yeast in a fluidized bed reactor

Continuous ethanol fermentation of glucose using fluidized bed technology was studied. Saccharomyces cerevisiae were immobilized and retained on porous microcarriers. Over two-thirds of the total reactor yeast cell mass was immobilized. Ethanol productivity was examined as dilution rate was varied, keeping all other experimental parameters constant. Ethanol yield remained high at an average of 0.36 g ethanol g^?1 glucose (71% of theoretical yield) as the dilution rate was increased stepwise from 0.04 h^?1 to 0.14 h^?1. At a dilution rate of 0.15 h^?1, the ethanol yield steeply declined to 0.22 g ethanol g^?1 glucose (44% of theoretical yield). The low maximum percentage of theoretical yield is primarily due to an extended mean cell residence time, and possibly due to the inhibitory effect of a high dissolved carbon dioxide concentration, enhanced by the probable intermittent levels of low pH in the reactor. Constant ethanol production was possible at a high glucose loading rate of 840 g dm^?3 day^?1 (attained at a dilution rate of 0.14 h^?1). Although the highest average ethanol concentration (97.14 g dm^?3) occurred at the initial dilution rate of 0.04 h^?1, the peak average ethanol production rate (2.87 g (g yeast)^?1 day^?1) was reached at a greater dilution rate of 0.11 ^h-1. Thus, the optimal dilution rate was determined to be between 0.11 h^?1 and 0.14 h^?1. Ethanol inhibition on yeast cells was absent in the reactor at average bulk-liquid ethanol concentrations as high as 97.14 g dm^?3. In addition, zero-order kinetics on ethanol production and glucose utilization was evident.     

Continuous production of thrombomodulin from a Pichia pastoris fermentation

A rotary membrane separation system was used in a continuous fermentation of Pichia pastoris with cell recycling to obtain high cell concentration and high thrombomodulin production. The dilution rates of this continuous fermentation were between 0·25 and 0·35 dm³ day⁻¹, and the production process was maintained for 10 days. Since cells were recycled and only part of liquid broth was taken from the system, a very high cell concentration level (248 g dm⁻³) was obtained. The peak protein expression level was at 72 h after methanol induction, was 300 mg dm⁻³ (3·6 × 10⁵ activity unit cm⁻³) and the total harvested supernatant was three times the working volume.