Enhancement of lactic acid production with ram horn peptone by Lactobacillus casei

Ram horns are a waste material from the meat industry. The use of ram horn peptone (RHP) as a supplement for lactic acid production was investigated using Lactobacillus casei. For this purpose, first, RHP was produced. Ram horns were hydrolysed by treating with acids (3 M H₂SO₄ and 6 M HCl) and neutralizing the solutions to yield ram horn hydrolysate (RHH). The RHH was evaporated to yield RHP. The amounts of protein, nitrogen, ash, some minerals, total sugars, total lipids and amino acids of the RHP were determined and compared with a bacto-tryptone from casein. When the concentrations (1–6% w/v) of the RHP were used in bacterial growth medium as a supplement, 2% RHP (ram horn peptone medium) had a maximum influence on the production of lactic acid by L. casei. The content of lactic acid in the culture broth containing 2% RHP (43 g l^–1) grown for 24 h was 30% higher than that of the control culture broth (33 g l^–1) and 10% higher than that of 2% bacto-tryptone (39 g l^–1). RHP was demonstrated to be a suitable supplement for production of lactic acid. This RHP may prove to be a valuable supplement in fermentation technology.     

Effect of lactic acid on diacetyl and acetoin production byLactobacillus casei subsp.rhamnosus ATCC 7469

Lactic acid or its acidity apparently play an important role in the regulation of the biosynthesis of flavor compounds inLactobacillus casei subsp.rhamnosus ATCC 7469. In pyruvate-containing media,L. casei produces lactic acid, acetoin, and diacetyl. A specific pH-dependent system is necessary for both the use of pyruvate and the induction of acetoin and diacetyl production. In cell extracts ofL. casei, lactic acid inhibits the enzymatic activity of acetolactate decarboxylase (ALD) and acetolactate synthetase (ALS); this effect does not occur in whole cells under standard physiological conditions. Lactic acid prevents the use of pyruvate, and the induction of acetoin and diacetyl production. When pyruvate-containing media are used, the pH must be kept close to 6.0 in order to obtain the best production of acetoin and diacetyl.     

Expression of a cloned cyclopropane fatty acid synthase gene reduces solvent formation in Clostridium acetobutylicum ATCC 824

The cyclopropane fatty acid synthase gene (cfa) of Clostridium acetobutylicum ATCC 824 was cloned and overexpressed under the control of the clostridial ptb promoter. The function of the cfa gene was confirmed by complementation of an Escherichia coli cfa-deficient strain in terms of fatty acid composition and growth rate under solvent stress. Constructs expressing cfa were introduced into C. acetobutylicum hosts and cultured in rich glucose broth in static flasks without pH control. Overexpression of the cfa gene in the wild type and in a butyrate kinase-deficient strain increased the cyclopropane fatty acid content of early-log-phase cells as well as initial acid and butanol resistance. However, solvent production in the cfa-overexpressing strain was considerably decreased, while acetate and butyrate levels remained high. The findings suggest that overexpression of cfa results in changes in membrane properties that dampen the full induction of solventogenesis. The overexpression of a marR homologous gene preceding the cfa gene in the clostridial genome resulted in reduced cyclopropane fatty acid accumulation.     

Inhibition of cyclopropane fatty acid synthase by sinefungin and A9145C

Sinefungin and A9145C, antifungal antibiotic analogs of S-adeno-sylmethionine isolated from $\text{Streptomyces}\text{,}\text{griseolus}$, have been found to be very effective $\text{in}\text{,}\text{vitro}$ inhibitors of cyclopropane fatty acid synthase from $\text{Lactobacillus}\text{,}\text{plantarum}$. Both compounds exhibit linear competitive inhibition with a K_i for Sinefungin of 220 nM and a K_i for A9145C of 11 nM.     

Influence of media composition on lactic acid production rate from whey by Lactobacillus helveticus

Summary The effect of preculture and culture media formulation on Lactobacillus helveticus lactic acid production rate was investigated in batch fermentations. Maximum lactic acid productivity of 5.5 g/l.h. was obtained from hydrolyzed whey. Clarified whey ultrafiltrate gave 4.4 g/l.h. at less expense.Nomenclature % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9qq-f0-yqaqVeLsFr0-vr% 0-vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaadaqdaaqaai% aab2eacaqGxbaaaaaa!3AF8!\[\overline {{\text{MW}}} \] peptides average molar weight - N_TK, N_NH2 total and primary -amino nitrogen concentrations (g/l) - p lactic acid concentration (g/l) - % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9qq-f0-yqaqVeLsFr0-vr% 0-vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaadaqdaaqaai% aabAfacaqGqbaaaaaa!3AFA!\[\overline {{\text{VP}}} \] lactic acid mean volumetric productivity (g/l.h.) - x total cell mass concentration (g/l)     

Influence of growth supplements on lactic acid production in whey ultrafiltrate by Lactobacillus helveticus

Summary Investigations have been carried out on lactic acid production by Lactobacillus helveticus CNRZ 303 in whey ultrafiltrate. Addition of beet molasses was investigated with good results, although yeast extract proved to be more effective. The size of inoculum and the preculture medium also played a significant role in determining the amount of lactic acid produced during the fermentation process. High lactose consumption (94.09%), together with good lactic acid production (26.09 g/l) and yield (0.90%), were obtained in whey ultrafiltrate supplemented with 1% (w/v) beet molasses (WUM), with a 10% (w/v) inoculum and peptonized milk as preculture medium. Although these results were similar to those obtained when yeast extract was used as supplement, the maximum volumetric productivities proved to be quite different, and were definitely higher with yeast extract. Offprint requests to: L. Chiarini     

Improvement of l-lactic acid production by osmotic-tolerant mutant of Lactobacillus casei at high temperature

l-Lactic acid production by Lactobacillus casei was used as a model to study the mechanism of substrate inhibition and the strategy for enhancing l-lactic acid production. It was found that the concentration of cell growth and l-lactate decreased with the increase of glucose concentration and fermentation temperature. To enhance the osmotic stress resistance of the strain at high temperature, a mutant G-03 was screened and selected with 360?g/L glucose at 45°C as the selective criterion. To further increase the cell growth for lactic acid production, 3?g/L of biotin was supplemented to the medium. As a result, l-lactate concentration by the mutant G-03 reached 198.2?g/L (productivity of 5.5?g?L^?1?h^?1) at 41°C in a 7-L fermentor with 210?g/L glucose as carbon source. l-Lactate concentration and productivity of mutant G-03 were 115.2% and 97.8% higher than those of the parent strain, respectively. The strategy for enhancing l-lactic acid production by increasing osmotic stress resistance at high temperature may provide an alternative approach to enhance organic acid production with other strains.     

Rapid screening of solvents and carrier compounds for lactic acid recovery by emulsion liquid extraction and toxicity on Lactobacillus casei (ATCC 11443)

This paper describes a rapid method to identify the best solvent and carrier compound combinations with the highest extraction capability and the lowest microbial toxicity characteristics for product recovery from microbial fermentation. The extraction system has an aqueous phase, and an emulsion phase, which was a blend of sodium carbonate and organic phase [91% (v/v) organic solvent, 5% (v/v or wt/v) carrier compound, and 4% (v/v) surfactant Span 80]. Alamine 336, or tri-n-octylamine in n-heptane; Alamine 336, Alamine 304, or tributyl phosphate in hexane; and Alamine 304 or tributyl phosphate in iso-octane; Alamine 304 or Amberlite in xylene demonstrated high lactic acid extraction. For determination of bacterial toxicity of selected solvent and carrier compounds, Lactobacillus casei subsp. rhamnosus (ATCC 11443) was grown in LAF medium containing one of the selected organic solvent, carrier compound, and Span 80 in 250 ml flask at 37 °C and 125 rpm. Samples were collected regularly during 48 hour incubation, and measured for changes in cell density by absorbance at 620 nm, cell count using a fluorescent dye with flow cytometry, and lactic acid, and glucose concentrations by HPLC. Hexadecane:tributyl phosphate, n-dodecane:tri-n-octylamine, and kerosene:tri-n-octylphosphine oxide demonstrated the least microbial toxicity among the tested blends with excess solvent media. Whereas, hexanes:Alamine 304 and xylenes:Alamine 304 were nontoxic in solvent saturated media.This revised version was published online in October 2005 with corrections to the Cover Date.     

Production of lactic acid from soybean stalk hydrolysate with Lactobacillus sake and Lactobacillus casei

In order to make full use of soybean stalk produced in large quantity annually in China, a process is proposed for production of lactic acid from soybean stalk hydrolysate with Lactobacillus sake and Lactobacillus casei. Experiments were conducted using the proposed process and experimental results indicate that the potential of 242 mg (g stalk)⁻¹ fermentable sugar is released from hydrolysate through enzymatic saccharication with a saccharication of 51%. The main sugar released from pretreated soybean stalk through enzymatic hydrolysis was a mixture of glucose, xylose and cellobiose at a ratio of 3.9:1.7:1. Fermentation of soybean stalk hydrolysate by L. sake and L. casei yielded the lactic acid conversion of 48% and 56%, respectively, however, lactic acid conversion increased to 71% by co-inoculation of both strains. L. sake and L. casei were able to degrade glucose, but unable to completely assimilate xylose and cellobiose. The proposed process can be used to produce lactic acid from soybean stalk hydrolysate.     

Evaluation of plastic-composite supports in repeated fed-batch biofilm lactic acid fermentation by Lactobacillus casei

A customized stirred-tank biofilm reactor was designed for plastic-composite supports (PCS). In repeated-batch studies, the PCS-biofilm reactors outperformed the suspended-cell reactors by demonstrating higher lactic acid productivities (2.45 g l(-1) h(-1) vs 1.75 g l(-1) h(-1)) and greater glucose consumption rates (3.27 g l(-1) h(-1) vs 2.09 g l(-1) h(-1)). In the repeated fed-batch studies, reactors were spiked periodically with concentrated glucose (75%) to maintain a concentration of approximately 80 g of glucose l(-1) in the bioreactor. In suspended-cell fermentations with 10 g of yeast extract (YE) l(-1) and zero, one, two, and three glucose spikes, the lactic acid productivities were 2.64, 1.58, 0.80, and 0.62 g l(-1) h(-1), respectively. In comparison, biofilm reactors with 7 g of YE l(-1) and zero, one, two, and three glucose spikes achieved lactic acid productivities of 4.20, 2.78, 0.66, and 0.94 g l(-1) h(-1), respectively. The use of nystatin (30 U ml(-1)) subdued the contaminating yeast population with no effect on the lactic acid productivity of the biofilm reactors, but it did affect productivity in the suspended-cell bioreactor. Overall, in repeated fed-batch fermentations, the biofilm reactors consistently outperformed the suspended-cell bioreactors, required less YE, and produced up to 146 g of lactic acid l(-1) with 7 g of YE l(-1), whereas the suspended-cell reactor produced 132 g l(-1) with 10 g of YE l(-1).     

Joint effect of nitrogen sources and B vitamin supplementation of date juice on lactic acid production by Lactobacillus casei subsp. rhamnosus

The use of date juice as a substrate for lactic acid production was investigated. Various nitrogen sources were compared with yeast extract for efficient lactic acid production by Lactobacillus casei subsp. rhamnosus. Among different nitrogen sources added to date juice (yeast extract, ammonium sulfate, tryptic soy, urea, peptone, and casein hydrolysate), yeast extract was the most efficient. The effect of yeast extract could have been due to its B vitamin content. The addition of five B vitamins at less than 25 mg/l to date juice with any nitrogen source enhanced lactic acid production to some extent, except for date juice with yeast extract or urea or peptone. The most significant increase was obtained with ammonium sulfate. Half of the yeast extract content (10 g/l) in a supplemented date juice could be replaced by a mixture of B vitamins at less than 25 mg/l, and ammonium sulfate at 2.6 g/l with no significant decrease in lactic acid production.     

Conditions required for citrate utilization during growth of Lactobacillus casei ATCC334 in chemically defined medium and Cheddar Cheese extract

Conditions required for citrate utilization by Lactobacillus casei ATCC334 were identified. Citrate was utilized by this microorganism in modified Chemically Defined Media (mCDM) as an energy source, solely in the presence of limiting concentrations of galactose. The presence of glucose inhibited citrate utilization by this microorganism even when added in limiting concentrations. Utilization of citrate occurred at pH 6.0 +/- 0.2 and 5.1 +/- 0.2. Together these observations suggest that citrate is an energy source for L. casei in ripening cheese only when the residual levels of carbohydrate post-fermentation are limiting (<2.5 mM), and lactose or glucose are absent. However, citrate utilization by this organism was observed in Cheddar cheese extract (CCE), which naturally contains both lactose and galactose, at the beginning of late-logarithmic phase and regardless of the galactose concentration present in the media.     

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).     

Influence of temperature on flavour compound production from citrate by Lactobacillus rhamnosus ATCC 7469

The citrate utilization by Lactobacillus rhamnosus ATCC 7469 was found to be temperature-dependent. The maximum citrate utilization and incorporation of [1,5-14C]citrate rate were observed at 37 degreesC. At this temperature, maximum citrate lyase activity and specific diacetyl and acetoin production (Y(DA%)) were observed. The high levels of alpha-acetolactate synthase and low levels of diacetyl reductase, acetoin reductase and L-lactate dehydrogenase found at 37 degreesC led to an accumulation of diacetyl and acetoin. Optimum lactic acid production was observed at 45 degreesC, according to the high lactate dehydrogenase activity. The NADH oxidase activity increased with increasing culture temperature from 22 degreesC to 37 degreesC. Thus there are greater quantities of pyruvate available for the production of alpha-acetolactate, diacetyl and aceotin, and less diacetyl and acetoin are reduced.