Rate Of Lactic Acid Production Research Articles

Acidosis and cancer: from mechanism to neutralization.

The extracellular pH of solid tumors is unequivocally acidic due to a combination of high rates of lactic acid production (a consequence of fermentative glycolytic metabolism) and poor perfusion. This has been documented by us and others in a wide variety of solid tumor models, primarily using magnetic resonance spectroscopic imaging (MRSI). This acidity contributes to tumor progression by inducing genome instability, promoting local invasion and metastases, inhibiting anti-tumor immunity, and conferring resistance to chemo- and radio-therapies. Systemic buffer therapies can neutralize tumor acidity and has been shown to inhibit local invasion and metastasis and improve immune surveillance in a variety of cancer model systems. This review will revisit the causes and consequences of acidosis by summarizing strategies used by cancer cells to adapt to acidosis, and how this acidity associated with carcinogenesis, metastasis, and immune function. Finally, this review will discuss how neutralization of acidity can be used to inhibit carcinogenesis and metastasis and improve anti-cancer immunotherapy.

Comparison of three commercially available buffy coat pooling sets for the preparation of platelet concentrates.

A disposable set for platelet concentrate (PC) preparation by the buffy coat method allows pooling of buffy coats, centrifugation and cell separation with in-line leucocyte filtration. This study compares three commercially available pooling sets in combination with INTERCEPT pathogen inactivation (PI). Sets for pooling of buffy coats were from Fresenius Kabi (FRE), Macopharma (MAC) and Terumo BCT (TER). Platelet yield, recovery and concentration were compared before and after PI (n = 20). Platelet quality was assessed by annexin V binding, P-selectin expression and PAC1 binding. The TER pooling set had the highest platelet yield (5·39 ± 0·44 × 1011 ) compared with MAC (4·53 ± 0·77) and FRE (4·56 ± 0·51) prior to PI. This was the result of a significantly higher platelet concentration in the TER storage bag (1·41 ± 0·12 × 106 /μL) compared with MAC (1·18 ± 0·19) and FRE (1·28 ± 0·15). However, the TER platelet content decreased by 15·6% after PI, yielding 4·55 ± 0·47 × 1011 platelets compared with smaller reductions at 9·5% for MAC (4·10 ± 0·69) and 4·4% for FRE (4·36 ± 0·52). None of the individual PC contained >106 leucocytes. The pH in TER PC was lower compared with MAC and FRE caused by a higher lactic acid production rate. Consequently, PAC1 binding after TRAP activation was lowest for TER PC on day 6. P-selectin and annexin V were not different between suppliers. This study demonstrates the added value of evaluating the entire component production process when introducing a new consumable. This study helped to inform a decision on what pooling set is ideally suited for routine implementation taking into account PI.

Optimization of lactic acid fermentation for pathogen inactivation in fecal sludge

The efficiency of lactic acid fermentation (LAF) as a pretreatment for human feces was investigated in laboratory-scale experiments that lasted for 3 weeks. The sanitization effect of LAF on fecal sludge (FS) was conducted in triplicate. This study used three materials, namely, lactobacillus of lactic acid bacteria, fermented cassava flour, and fermented rice flour, which were known to enhance the production of lactic acid. Each material was mixed in three different reactors at equal ratio with raw FS (i.e., 1:1 v/w, w/w, and w/w). The pH decline rate, lactic acid production rate, and fecal coliform suppression degree were monitored over the period of the treatment process as parameters to evaluate the efficiency of various LAF for pathogen inactivation in FS. Results showed that only fermented rice flour was able to completely inactivate the indicator organism (fecal coliform) at the end of fermentation. Final plate counts of 8.6 × 108 CFU/100 mL, 2.4 × 108 CFU/100 mL, and zero (0) were achieved from lactobacillus, fermented cassava flour, and fermented rice flour treatment processes, respectively. The final pH from the reactors that contained lactobacillus and FS, cassava flour and FS, and fermented rice flour and FS were 5.5, 8, and 3.9, respectively. This study revealed that not all LAF materials can effectively suppress pathogens in FS. The results serve as the foundation in developing an effective, cheap, and easy to use LAF on FS pretreatment for pathogen inactivation.

Temperature-Phased Conversion of Acid Whey Waste Into Medium-Chain Carboxylic Acids via Lactic Acid: No External e-Donor

Summary Acid whey is a Greek-yogurt waste stream and can be a resource to produce biofuel precursors. Our objective was to convert acid whey into medium-chain carboxylic acid (MCCA) oil with the open-culture carboxylate platform. Here, we developed a temperature-phased bioprocess with different anaerobic reactor microbiomes, performing thermophilic lactic acid production and mesophilic chain elongation, to produce MCCAs (C6–C9) from acid whey via lactic acid as an intermediate. For the lactic acid-producing bioreactor, we achieved a volumetric lactic acid production rate of 1,230 mmol C L −1 day −1 (1.54 g L −1 hr −1 ). For the chain-elongating bioreactor, we achieved a volumetric MCCA production rate of 111 mmol C L −1 day −1 and a volumetric n -caproic acid (C6) production rate of 81 mmol C L −1 day −1 (0.07 g L −1 hr −1 ). We converted a real waste stream into mainly MCCAs without the external addition of an electron donor.

Scaling-up of simultaneous saccharification and fermentation of lactic acid from microwave-alkali-treated empty fruit bunches

The goal of this work was to scale up the simultaneous saccharification and fermentation (SSF) of lactic acid using microwave-alkali-pretreated empty fruit bunches (EFB) from a scale of 16 L to a scale of 150 L. To facilitate the scaling-up process of lactic acid production by Rhizopus oryzae NRRL 395, a scaling-up criterion of constant kLa value was applied. Operating conditions, such as aeration rate and superficial velocity, were varied and evaluated on both scales (16-L and 150-L). The highest lactic acid yield of 6.8 g/L was obtained under an operating condition of 1 vvm (0.061 s-1). Parallel aeration rates were determined for the 150-L fermenter system to obtain the same kLa value as the 16-L fermenter. An operational condition of 0.5 vvm dissolved oxygen supply in the 150-L fermenter was optimal to support an identical value of kLa and production rate of lactic acid for both scales.

A Case Report of Severe Type B Lactic Acidosis Following First Dose of Nivolumab in a VHL-Mutated Metastatic Renal Cell Carcinoma.

We report a case of severe type B lactic acidosis (LA) in a 51-year-old male, 12 days after he received his first dose of nivolumab for metastatic Von Hippel Lindau (VHL)-mutated, clear cell renal cell carcinoma. Throughout his hospital course, infection, hypoperfusion, and tissue necrosis were not identified. We propose that his LA may have resulted from either inherent tumor glycolysis or immune activation and enhanced metabolism. The patient’s course was complicated by acute renal failure, and his LA rose progressively, eventually necessitating daily hemodialysis (HD). After receiving five consecutive days of HD, the patient started everolimus daily with the intent of reducing glycolytic metabolism. Subsequently, the rate of lactic acid production slowed, and HD was no longer required after two doses of everolimus. To our knowledge, this is the first reported case of type B LA following nivolumab administration, and the use of everolimus to treat type B LA in a patient with renal cancer.

Direct Solid Lewis Acid Catalyzed Wood Liquefaction into Lactic Acid: Kinetic Evidences that Wood Pretreatment Might Not be a Prerequisite

AbstractThe objective of the present work was to determine if wood sawdust can be used instead of isolated cellulose in the general solid‐acid‐catalyzed production of chemicals. The kinetics of model cellulose and pine‐wood sawdust liquefaction into lactic acid were determined in the presence of a solid Lewis acid, ZrW. The catalytic hydrolysis of pine wood was performed at 190 °C in a large‐scale batch reactor (2.5 L). Similar kinetic curves of lactic formation were obtained for cellulose and wood as substrates. Moreover, the initial lactic acid production rate of pine‐wood sawdust was higher than that of model cellulose, proving that, in spite of the presence of lignin/hemicellulose, the catalyst drives the transformation towards lactic acid formation. However, our results give also evidence of solid‐catalyst deactivation for both cellulose and wood substrates. This result indicates that if wood pretreatment can be bypassed, the bottleneck will be the solid‐catalyst regeneration and recycling.

Stable shRNA Silencing of Lactate Dehydrogenase A (LDHA) in Human MDA-MB-231 Breast Cancer Cells Fails to Alter Lactic Acid Production, Glycolytic Activity, ATP or Survival.

In the US, African Americans have a high death rate from triple-negative breast cancer (TNBC), characterized by lack of hormone receptors (ER, PR, HER2/ERRB2) which are otherwise valuable targets of chemotherapy. There is a need to identify novel targets that negatively impact TNBC tumorigenesis. TNBCs release an abundance of lactic acid, under normoxic, hypoxic and hyperoxic conditions; this referred to as the Warburg effect. Accumulated lactic acid sustains peri-cellular acidity which propels metastatic invasion and malignant aggressive transformation. The source of lactic acid is believed to be via conversion of pyruvate by lactate dehydrogenase (LDH) in the last step of glycolysis, with most studies focusing on the LDHA isoform. In this study, LDHA was silenced using long-term MISSION® shRNA lentivirus in human breast cancer MDA-MB-231 cells. Down-regulation of LDHA transcription and protein expression was confirmed by western blot, immunocytochemistry and qPCR. A number of parameters were measured in fully viable vector controls versus knock-down (KD) clones, including levels of lactic acid produced, glucose consumed, ATP and basic metabolic rates. The data show that lentivirus V-165 generated a knock-down clone most effective in reducing both gene and protein levels to less than 1% of vector controls. Stable KD showed absolutely no changes in cell viability, lactic acid production, ATP, glucose consumption or basic metabolic rate. Given the complete absence of impact on any observed parameter by LDH-A KD and this being somewhat contrary to findings in the literature, further analysis was required to determine why. Whole-transcriptome analytic profile on MDA-MB-231 for LDH subtypes using Agilent Human Genome 4×44k microarrays, where the data show the following component breakdown. Transcripts: 30.47 % LDHA, 69.36% LDHB, 0.12% LDHC and 0.05% LDHD. These findings underscore the importance of alternative isoforms of LDH in cancer cells to produce lactic acid, when LDHA is silenced or inhibited. LDHA silencing alone is not effective in hampering or inducing changes in survival, metabolism or lactic acid produced in a cell line with high concentrations of LDHB. Future research will be required to confirm effects of dual LDHA/B knockdown and further confirm that the sole source of lactic acid produced occurs through LDH (all isoforms) in breast cancer cells.

Extended storage of cold raw milk on yogurt manufacturing

Abstract: The objective of this work was to evaluate the effect of the extended cold storage of raw milk on the kinetics of fermentation on yogurt production, as well as on the product’s microbiological and physicochemical properties during shelf life. Three treatments were evaluated: yogurts made with raw milk stored for 4, 72, and 168 hours. Kinetics of fermentation was assessed through the lactic acid production rate, growth rate of Streptococcus thermophilus and Lactobacillus bulgaricus, and time to reach pH 5.0 and 4.5. The physicochemical and microbiological characteristics of raw milk and yogurts were also analyzed during cold storage at 4°C. The microbial quality of raw milk was affected by the storage time of 168 hours, with a decreasing tendency in the mesophiles:psychrotrophs ratio. Extended storage of raw milk beyond 72 hours negatively affects yogurt production, despite the low initial bacterial count, decreasing lactic acid production, S. thermophilus growth rate, pH, and protein content. Therefore, to optimize fermentation and yogurt shelf life, the maximum storage time for raw milk at 4oC should not exceed 72 hours.

Effect of polyphenols on glucose and lactate transport by breast cancer cells.

One of the cancer molecular hallmarks is a deviant energetic metabolism, known as the Warburg effect, whereby the rate of glucose uptake is significantly increased and a high rate of glycolysis and lactic acid production occurs even when oxygen is present-"aerobic lactatogenesis". Accordingly, GLUT1 and MCT1, which are the main glucose and lactate transporters in cancer cells, respectively, have been proposed as oncogenes and are currently seen as potential therapeutic targets in cancer treatment. Polyphenols, commonly contained in fruits and vegetables, have long been associated with a protective role against cancer. Generally considered as nontoxic, dietary polyphenols are considered ideal chemopreventive and possibly chemotherapeutic agents. Several mechanisms of action of polyphenols in breast cancer cells have been proposed including modulation of intracellular signaling, induction of apoptosis through redox regulation or modulation of epigenetic alterations. Additionally, in vitro studies have shown that several polyphenols act as specific inhibitors of glucose transport in breast cancer cell lines and an association between their anticarcinogenic effect and inhibition of glucose cellular uptake has been described. Also, some polyphenols were found to inhibit lactate transport. Importantly, some polyphenols behave as inhibitors of both glucose and lactate cellular uptake by breast cancer cells and these compounds are thus very interesting in the context of a chemopreventive effect, because they deplete breast cancer cells of their two most important energy suppliers. So, the antimetabolic effect of polyphenols should be regarded as a mechanism of action contributing to their chemopreventive/chemotherapeutic potential in relation to breast cancer.

Effect of Electrical Stimulation on Grasshopper Jumping Muscle

Skeletal muscles can undergo biochemical and physiological changes due to exercise training. For example, aerobic exercise training may lead to an increased mitochondria volume, a higher proportion of slow twitch myosin ATPase, and a reduced rate of lactic acid production. Similar changes in mammalian muscle have also been demonstrated using electrical stimulation. However, it is unclear if invertebrate muscle also responds to training or electrical stimulation. We examine whether Schistocerca americana grasshopper jumping muscles are affected by electrical stimulation. Grasshopper jumping muscle is one of the few invertebrate muscles to produce lactic acid during locomotion. Electrical probe leads are placed near the coxa on the ventral side of the animal. The muscle was stimulated with a single pulse width of 2 ms at 0.075 V and repeated at a frequency of 100 Hz. We electrically stimulate the entire jumping muscle, including both the flexor and the extensor, to elicit continuous muscle contractions in a single metathoracic leg. To invoke a training response, a grasshopper is stimulated for 5 hours daily for 5 consecutive days. The lactate production rate of trained and untrained grasshopper muscle will then be fluorometrically measured after 5 min, 30 min, 60 min, 180 min, or 300 min of electrical stimulation. We predict that repeated stimulation would alter the rate of lactic acid production. Since grasshopper jumping muscle is similar to human muscle, this research may provide insight into fundamental questions about muscle plasticity.Support or Funding InformationUnion College Undergraduate Research Committee

Bioaugmentation of Lactobacillus delbrueckii ssp. bulgaricus TISTR 895 to enhance bio-hydrogen production of Rhodobacter sphaeroides KKU-PS5.

BackgroundBioaugmentation or an addition of the desired microorganisms or specialized microbial strains into the anaerobic digesters can enhance the performance of microbial community in the hydrogen production process. Most of the studies focused on a bioaugmentation of native microorganisms capable of producing hydrogen with the dark-fermentative hydrogen producers while information on bioaugmentation of purple non-sulfur photosynthetic bacteria (PNSB) with lactic acid-producing bacteria (LAB) is still limited. In our study, bioaugmentation of Rhodobacter sphaeroides KKU-PS5 with Lactobacillus delbrueckii ssp. bulgaricus TISTR 895 was conducted as a method to produce hydrogen. Unfortunately, even though well-characterized microorganisms were used in the fermentation system, a cultivation of two different organisms in the same bioreactor was still difficult because of the differences in their metabolic types, optimal conditions, and nutritional requirements. Therefore, evaluation of the physical and chemical factors affecting hydrogen production of PNSB augmented with LAB was conducted using a full factorial design followed by response surface methodology (RSM) with central composite design (CCD).ResultsA suitable LAB/PNSB ratio and initial cell concentration were found to be 1/12 (w/w) and 0.15 g/L, respectively. The optimal initial pH, light intensity, and Mo concentration obtained from RSM with CCD were 7.92, 8.37 klux and 0.44 mg/L, respectively. Under these optimal conditions, a cumulative hydrogen production of 3396 ± 66 mL H2/L, a hydrogen production rate (HPR) of 9.1 ± 0.2 mL H2/L h, and a hydrogen yield (HY) of 9.65 ± 0.23 mol H2/mol glucose were obtained. KKU-PS5 augmented with TISTR 895 produced hydrogen from glucose at a relatively high HY, 9.65 ± 0.23 mol H2/mol glucose, i.e., 80 % of the theoretical yield.ConclusionsThe ratio of the strains TISTR 895/KKU-PS5 and their initial cell concentrations affected the rate of lactic acid production and its consumption. A suitable LAB/PNSB ratio and initial cell concentration could balance the lactic acid production rate and its consumption in order to avoid lactic acid accumulation in the fermentation system. Through use of appropriate environmental conditions for bioaugmentation of PNSB with LAB, a hydrogen production could be enhanced.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0375-z) contains supplementary material, which is available to authorized users.

Advanced green biorefining: effects of ensiling treatments on lactic acid production, microbial activity and supplementary methane formation of grass and rye

For a more eco-friendly production of energy and chemicals (e.g. lactic acid), green biorefineries are implementing an environmentally conscious technique of using green biomass. To increase the amount of lactic acid in grass and rye silage, different ensiling treatments were conducted. Additionally, after separating the organic juice, the specific methane yield of the remaining solid residue of the ensiled material was determined. The amount of lactic acid was increased by 168.8 % (149.7 ± 20.9 g kg−1 dry matter (DM)) through applying homofermentative lactic acid bacteria together with carbonated lime to the raw material grass. For rye, while having a stable silage, the highest increase in lactic acid was achieved by chopping the raw material to a theoretical length of cut of 1 mm. As a result, an increase of 46.3 % (57.5 ± 0.6 g kg−1 DM) was attained. Taxonomic profiling by 16S amplicon sequencing revealed that the homofermentative species Lactobacillus plantarum was the most dominant species on both substrates with highest lactic acid production rate, though its growth on rye led to unstable silage conditions with butyric acid producing Clostridia. The specific methane yields of the corresponding solid residues were determined to be 335.7 ± 7.2 lN kg−1 organic dry matter (ODM) for grass and at 235.0 ± 2.6 lN kg−1 ODM for rye.

Glucose Addiction in Cancer Therapy: Advances and Drawbacks.

While normal differentiated cells primarily use mitochondrial respiration to generate the required energy for cellular processes, most cancer cells rely on glycolysis, even in sufficient oxygen conditions. This phenomenon is known as the "Warburg effect" or aerobic glycolysis and the metabolic reprogramming of cancer cells towards this altered energy metabolism is currently recognized as one of the "hallmarks of cancer". Aerobic glycolysis underlies the rapid growth of tumor cells, with high rates of glucose consumption and lactic acid production, leading to cellular acidosis. Metabolic reprogramming renders cancer cells dependent on specific metabolic enzymes or pathways that could be exploited in cancer therapy. The development of treatments that target tumor glucose metabolism is receiving renewed attention, with several drugs targeting metabolic pathways currently in clinical trials. The search for suitable targets, however, is limited by the high plasticity of the metabolic network that can induce compensatory routes. Deregulated glucose metabolism is a prominent feature associated with resistance to classical chemotherapy or oncogene-targeted therapies, strengthening the clinical potential of combining these therapies with glycolysis inhibitors. The aim of this review is to compare the advances of different therapeutic strategies targeting the glucose "addiction" of tumor cells, highlighting their potential as effective weapons against cancer. We further discuss recent evidence for the involvement of glucose metabolism as a compensatory response to the use of drugs that target different signaling pathways, where the combination with glycolysis inhibitors could prove extraordinarily useful.

Ultraviolet C light pathogen inactivation treatment of platelet concentrates preserves integrin activation but affects thrombus formation kinetics on collagen in vitro.

Ultraviolet (UV) light illumination in the presence of exogenously added photosensitizers has been used to inactivate pathogens in platelet (PLT) concentrates for some time. The THERAFLEX UV-C system, however, illuminates PLT concentrates with UV-C light without additional photoactive compounds. In this study residual PLT function is measured in a comprehensive paired analysis of UV-C-treated, gamma-irradiated, and untreated control PLT concentrates. A pool-and-split design was used with buffy coat-derived PLT concentrates in 65% SSP+ additive solution. Thrombus formation kinetics in microfluidic flow chambers onto immobilized collagen was investigated with real-time video microscopy. PLT aggregation, membrane markers, and cellular metabolism were determined concurrently. Compared to gamma-treated and untreated controls, UV-C treatment significantly affected thrombus formation rates on Days5 and 7, not Day2. PLT degranulation (P-selectin) and PLT apoptosis (annexinV binding) was slightly but significantly increased from Day2 on. UV-C treatment moreover induced integrin αIIb β3 conformational changes reminiscent of activation. However, subsequent integrin activation by either PAR1-activating hexapeptide (PAR1AP) or convulxin was unaffected. This was confirmed by PLT aggregation studies induced with collagen, PAR1AP, and ristocetin at two different agonist concentrations. Finally, UV-C slightly increased lactic acid production rates, resulting in significantly decreased pH on Days5 and 7, but never dropped below 7.2. UV-C pathogen inactivation treatment slightly but significantly increases PLT activation markers but does not profoundly influence activatability nor aggregation. The treatment does, however, attenuate thrombus formation kinetics in vitro in microfluidic flow chambers, especially after storage.

Metabolism and its sequelae in cancer evolution and therapy.

Cancers progress through a series of events that can be characterized as "somatic evolution." A central premise of Darwinian evolutionary theory is that the environment imparts pressure to select for species that are most fit within that particular microenvironmental context. Furthermore, the rate of evolution is proportional to both (1) the strength of the environmental selection and (2) the phenotypic variance of the selected population. It is notable that, during the progression of cancers from carcinogenesis to local invasion to metastasis, the selective landscape continuously changes, and throughout this process, there is increased selection for cells that have altered metabolic phenotypes: implying that these phenotypes impart a selective advantage during the process of environmental selection. One of the most prevalent selected phenotypes is that of aerobic glycolysis, that is, the continued fermentation of glucose even in the presence of adequate oxygen. The mechanisms of this so-called "Warburg effect" have been well studied, and there are multiple models to explain how this occurs at the molecular level. Herein, we propose that unifying insights can be gained by evaluating the environmental context within which this phenotype arises. In other words, we focus not on the "how" but the "why" do cancer cells exhibit high aerobic glycolysis. This is best approached by examining the sequelae of aerobic glycolysis that may impart a selective advantage. Many of these have been considered, including generation of anabolic substrates, response rates of glycolysis vis-à-vis respiration, and generation of antioxidants. A further sequeala considered here is that aerobic glycolysis results in a high rate of lactic acid production; resulting in acidification of the extracellular space. Indeed, it has been shown that a low extracellular pH promotes local invasion, promotes metastasis, and inhibits antitumor immunity. In naturally occurring cancers, low extracellular pH is a strong negative prognostic indicator of metastasis-free survival. Furthermore, it has been shown that inhibition of extracellular acidosis can inhibit metastasis and promote antitumor immunity. Hence, we propose that excess acid production confers a selective advantage for cells during the somatic evolution of cancers.

Dependence of growth characteristics of original strains of Lactococcus lactis subsp. lactis on the composition of agar media used for biomass growth

Data on the dependence of growth characteristics of Lactococcus lactis subsp. lactis 729 and TB2 extracted from milk and homemade curd on the content of casein peptone (CP) as the main source of nitrogen in the agar medium is presented. The number of colony-forming units (CFUs), cell division rate (CDR), and mean hourly doubling time (HDT) were compared between two time segments of cultivation: from 1 to 2.5 h, and from 2.5 to 3.5 h. In liquid media, logarithmic growth was observed for the 729 strain in all groups for 3.5 h at minimal pH of 6.5. The maximum biomass production rate (2.5 × 108 cells/mL) was observed in the media containing the meat extract; the minimal HDT was in the biomass transferred from the minimal MA4 medium to the enriched M7 medium. In contrast with the TB2 strain, the 729 strain does not form colonies on agar media at CP concentrations below 0.4%. The colonies of the TB2 strain increase in size from 2.85 mm2 to 5 mm2 when decreasing CP concentration from 1 to 0.4%. The yeast extract has a stimulating effect in liquid media at said concentration ratios, leading to an increase in the efficiency of cell division at lower rates of lactic acid production, to pH of 5.5 when oligopeptide transport is blocked. The meat extract provides adaptation of bacteria to the conditions of excessive acidity and has positive effect on cell division in the 729 strain at later stages of bacterial colony development. The smaller size of colonies of the strain might be evidence of active acid formation.

Adaptive Control of Lactic Acid Production Process from Wheat Flour

The key feature of this paper is the development of a control strategy for the lactic acid production process from wheat flour in a continuous bioreactor. As lactic acid has inhibition effects on bacterial growth and its own production, the regulation of its concentration is required. In this paper, a control strategy is proposed in order to maximize the process productivity. First, the optimal setpoint is determined. Then, a controller based on a state-feedback linearizing control strategy is proposed to regulate the product concentration at its optimal value. The developed control law requires measurement or estimation of online state variables and a good knowledge of model parameters. In this paper the estimation of lactic acid production rate is proposed as an alternative to reduce the complexity of the control law. Different production rate estimators are studied and tested. Finally, the proposed control strategy results in a controller that involves the estimation of the production rate by a Kalman filter. The effectiveness of the developed strategy is illustrated by simulation results.

Optimization of Fermented Tofu with High Isoflavone Content through Variation of Inoculum Percentages and Ratios of Lactobacillus plantarum, Lactobacillus acidophilus, and Leuconostoc mesenteroides

Tofu is a traditional food that can be found in several countries, such as Indonesia and Japan. Tofu is often made using the backslopping method, which brings the risk of pathogenic microorganism contamination and can lead to failure in production. Standardization of the production process is necessary in order to yield highly nutritious tofu that is safe to be consumed. In this research, standardization was investigated by variation of the inoculum percentages and ratios of Lactobacillus plantarum (a), Lactobacillus acidophilus (b), and Leuconostoc mesenteroides (c). The inoculum percentages used in this research were 7.5%, 10%, and 12.5%, while the inoculum ratios between a, b, and c were (a:b:c) 2:1:1; 1:2:1; 1:1:2; and 1:1:1. The optimum inoculum ages for a, b, and c were 8, 6, and 2 hours respectively. The highest growth rates of a, b, and c were 0.060h-1, 0.054h-1, and 0.092h-1 respectively. The highest lactic acid production rates of a, b, and c were 0.072%h-1, 0.063%h-1, and 0.126%h-1 respectively. The inoculum percentage and ratio that produced the highest isoflavones content was 12.5%(2:1:1), with the highest bacterial population growth rate being 0.019h-1, the highest formation rate of lactic acid being 0.045%h-1, and the isoflavone aglycones level being 0.445 mg/mL.

Unstructured kinetic modeling of growth and lactic acid production by Lactobacillus plantarum NCDC 414 during fermentation of vegetable juices

Unstructured Gompertz and Logistic models were developed to describe growth, substrate utilization and lactic acid production by Lactobacillus plantarum NCDC 414 in juices of bitter gourd (Momordica charantia), bottle gourd (Lagenaria siceraria) and carrot (Daucus carota). These vegetable juices have considerably good quantities of total sugars that allowed the growth of L. plantarum for 24 h at 37 °C, after which the cell numbers begin to decline. Kinetics of cell growth, lactic acid production and sugar consumption were evaluated. The viable cell counts increased from 4 × 105 CFU/ml to 7 × 1010 CFU/ml after 24 h of fermentation. The lactic acid increased by about 4.5 times in 24 h and about 44% w/v reduction in sugar content was observed during growth of L. plantarum. Significant lactic acid production occurred during the growth phase as well as stationary phase. With the kinetic model proposed by R. Luedeking and E.L. Piret for lactic acid production rate, the growth associated and non growth associated coefficients were determined. The model was demonstrated for batch growth of L. plantarum in vegetable juice.