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

Cardenas, I. L. Benito De; Ledesma, O; Oliver, G.

doi:10.1007/bf01571127

Cited by 7 publications

(6 citation statements)

References 7 publications

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“…A similar pH optimum was reported by Størmer (1977) for acetolactate synthase derived from Aerobacter aerogenes. These results have been verified more recently by Benito de Cardenas et al (1989) and Monnet et al (1994) in strains of Lactobacillus casei and Lactococcus lactis, respectively. The pH sensitivity of the acetolactate enzyme was also demonstrated in metabolic engineering studies of L. lactis where a greater than 2-fold difference in pyruvate conversion to acetoin was reported in the pH range 6.0-6.8 (Platteeuw et al, 1995).…”

Section: Dependence Of the Activity Of Acetoin And 23-butanediol-forsupporting

confidence: 58%

Scale‐down model to simulate spatial pH variations in large‐scale bioreactors

Amanullah

McFarlane

Emery

et al. 2001

Biotech & Bioengineering

136

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For the first time a laboratory-scale two-compartment system was used to investigate the effects of pH fluctuations consequent to large scales of operation on microorganisms. pH fluctuations can develop in production-scale fermenters as a consequence of the combined effects of poor mixing and adding concentrated reagents at the liquid surface for control of the bulk pH. Bacillus subtilis was used as a model culture since in addition to its sensitivity to dissolved oxygen levels, the production of the metabolites, acetoin and 2,3-butanediol, is sensitive to pH values between 6.5 and 7.2. The scale-down model consisted of a stirred tank reactor (STR) and a recycle loop containing a plug flow reactor (PFR), with the pH in the stirred tank being maintained at 6.5 by addition of alkali in the loop. Different residence times in the loop simulated the exposure time of fluid elements to high values of pH in the vicinity of the addition point in large bioreactors and tracer experiments were performed to characterise the residence time distribution in it. Since the culture was sensitive to dissolved oxygen, for each experiment with pH control by adding base into the PFR, equivalent experiments were conducted with pH control by addition of base into the STR, thus ensuring that any dissolved oxygen effects were common to both types of experiments. The present study indicates that although biomass concentration remained unaffected by pH variations, product formation was influenced by residence times in the PFR of 60 sec or longer. These changes in metabolism are thought to be linked to both the sensitivity of the acetoin and 2,3-butanediol-forming enzymes to pH and to the inducing effects of dissociated acetate on the acetolactate synthase enzyme.

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Section: Dependence Of the Activity Of Acetoin And 23-butanediol-forsupporting

confidence: 58%

Scale‐down model to simulate spatial pH variations in large‐scale bioreactors

Amanullah

McFarlane

Emery

et al. 2001

Biotech & Bioengineering

136

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“…Further, the decreased lactic acid concentration in the three stage process also enhances flavor production, since it is reported that lactic acid has a negative effect over flavor formation [9]. The pyruvate concentration in the medium also increased to 30 mM, indicating activation of diacetyl and acetoin synthesis [6,9]. Thus, intermittent addition of starch enhanced the production of flavor substantially.…”

Section: Resultsmentioning

confidence: 85%

“…Since L. rhamnosus could metabolize citrate, another strategy that was used to enhance flavor synthesis was the addition of citrate into the SSF medium. The organism could metabolize citrate in presence of glucose and the excess pyruvate synthesized was directed towards the synthesis of flavors [6]. The structured model incorporated the consumption of multiple substrates and could predict the SSF process with addition of citrate in to the medium.…”

Section: Resultsmentioning

confidence: 99%

Modeling and experimental studies on intermittent starch feeding and citrate addition in simultaneous saccharification and fermentation of starch to flavor compounds

Chavan

Raghunathan

Venkatesh

2009

J Ind Microbiol Biotechnol

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Simultaneous saccharification and fermentation (SSF) is a combined process of saccharification of a renewable bioresource and fermentation process to produce products, such as lactic acid and ethanol. Recently, SSF has been extensively used to convert various sources of cellulose and starch into fermentative products. Here, we present a study on production of buttery flavors, namely diacetyl and acetoin, by growing Lactobacillus rhamnosus on a starch medium containing the enzyme glucoamylase. We further develop a structured kinetics for the SSF process, which includes enzyme and growth kinetics. The model was used to simulate the effect of pH and temperature on the SSF process so as to obtain optimum operating conditions. The model was experimentally verified by conducting SSF using an initial starch concentration of 100 g/L. The study demonstrated that the developed kinetic was able to suggest strategies for improved productivities. The developed model was able to accurately predict the enhanced productivity of flavors in a three stage process with intermittent addition of starch. Experimental and simulations demonstrated that citrate addition can also lead to enhanced productivity of flavors. The developed optimal model for SSF was able to capture the dynamics of SSF in batch mode as well as in a three stage process. The structured kinetics was also able to quantify the effect of multiple substrates present in the medium. The study demonstrated that structured kinetic models can be used in the future for design and optimization of SSF as a batch or a fed-batch process.

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“…MATERIALS & METHODS CERTAIN LACTIC ACID BACTERIA convert citrate to diacetyl (DA) through a pyruvate intermediate (Banito de Cardenas et al, 1985, 1989Branen and Keenan, 1971a, b). DA plays a productive role in flavor for many dairy fermentations.…”

Section: Introductionmentioning

confidence: 99%

Diacetyl Measurement in Orange Juice Using Differential Pulse Polarography

Sadler¹,

Parish²,

Davis³

1990

Journal of Food Science

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Reconstituted single strength orange juice was distilled to recover diacetyl. 0.5 mL of 1N LiOH was added to 4.5 mL of distillate. Using a static mercury drop electrode, a current vs potential scan was performed between -0.7 and -1.10 vs an Ag/AgCI reference electrode. The reduction potential for diacetyl was -0.83 V. Peak heights were proportional to concentration throughout the test range (8.3 ppb to 1 ppm). Diacetyl recoveries were approximately 85%.

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

Cited by 7 publications

References 7 publications

Scale‐down model to simulate spatial pH variations in large‐scale bioreactors

Scale‐down model to simulate spatial pH variations in large‐scale bioreactors

Modeling and experimental studies on intermittent starch feeding and citrate addition in simultaneous saccharification and fermentation of starch to flavor compounds

Diacetyl Measurement in Orange Juice Using Differential Pulse Polarography

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