scholarly journals Relationship between pH and Medium Dissolved Solids in Terms of Growth and Metabolism of Lactobacilli and Saccharomyces cerevisiae during Ethanol Production

2005 ◽  
Vol 71 (5) ◽  
pp. 2239-2243 ◽  
Author(s):  
Neelakantam V. Narendranath ◽  
Ronan Power
Keyword(s):  
Growth Rate ◽  
Lactic Acid ◽  
Specific Growth Rate ◽  
Ethanol Production ◽  
Growth Rates ◽  
Specific Growth ◽  
Lactic Acid Production ◽  
Good Practice ◽  
Medium Ph ◽  
Dissolved Solids

ABSTRACT The specific growth rates of four species of lactobacilli decreased linearly with increases in the concentration of dissolved solids (sugars) in liquid growth medium. This was most likely due to the osmotic stress exerted by the sugars on the bacteria. The reduction in growth rates corresponded to decreased lactic acid production. Medium pH was another factor studied. As the medium pH decreased from 5.5 to 4.0, there was a reduction in the specific growth rate of lactobacilli and a corresponding decrease in the lactic acid produced. In contrast, medium pH did not have any significant effect on the specific growth rate of yeast at any particular concentration of dissolved solids in the medium. However, medium pH had a significant (P < 0.001) effect on ethanol production. A medium pH of 5.5 resulted in maximal ethanol production in all media with different concentrations of dissolved solids. When the data were analyzed as a 4 (pH levels) by 4 (concentrations of dissolved solids) factorial experiment, there was no synergistic effect (P > 0.2923) observed between pH of the medium and concentration of dissolved solids of the medium in reducing bacterial growth and metabolism. The data suggest that reduction of initial medium pH to 4.0 for the control of lactobacilli during ethanol production is not a good practice as there is a reduction (P < 0.001) in the ethanol produced by the yeast at pH 4.0. Setting the mash (medium) with ≥30% (wt/vol) dissolved solids at a pH of 5.0 to 5.5 will minimize the effects of bacterial contamination and maximize ethanol production by yeast.

scholarly journals Effect of Specific Growth Rate on Fermentative Capacity of Baker’s Yeast

1998 ◽  
Vol 64 (11) ◽  
pp. 4226-4233 ◽  
Author(s):  
Pim Van Hoek ◽  
Johannes P. Van Dijken ◽  
Jack T. Pronk
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Ethanol Production ◽  
Growth Rates ◽  
Specific Growth ◽  
Pyruvate Decarboxylase ◽  
Baker's Yeast ◽  
Fermentative Capacity ◽  
Yeast Biomass ◽  
Specific Growth Rates

ABSTRACT The specific growth rate is a key control parameter in the industrial production of baker’s yeast. Nevertheless, quantitative data describing its effect on fermentative capacity are not available from the literature. In this study, the effect of the specific growth rate on the physiology and fermentative capacity of an industrialSaccharomyces cerevisiae strain in aerobic, glucose-limited chemostat cultures was investigated. At specific growth rates (dilution rates, D) below 0.28 h−1, glucose metabolism was fully respiratory. Above this dilution rate, respirofermentative metabolism set in, with ethanol production rates of up to 14 mmol of ethanol · g of biomass−1 · h−1at D = 0.40 h−1. A substantial fermentative capacity (assayed offline as ethanol production rate under anaerobic conditions) was found in cultures in which no ethanol was detectable (D < 0.28 h−1). This fermentative capacity increased with increasing dilution rates, from 10.0 mmol of ethanol · g of dry yeast biomass−1 · h−1 at D= 0.025 h−1 to 20.5 mmol of ethanol · g of dry yeast biomass−1 · h−1 atD = 0.28 h−1. At even higher dilution rates, the fermentative capacity showed only a small further increase, up to 22.0 mmol of ethanol · g of dry yeast biomass−1 · h−1 at D= 0.40 h−1. The activities of all glycolytic enzymes, pyruvate decarboxylase, and alcohol dehydrogenase were determined in cell extracts. Only the in vitro activities of pyruvate decarboxylase and phosphofructokinase showed a clear positive correlation with fermentative capacity. These enzymes are interesting targets for overexpression in attempts to improve the fermentative capacity of aerobic cultures grown at low specific growth rates.

scholarly journals Mathematical Modeling of Lactobacillus paracasei CBA L74 Growth during Rice Flour Fermentation Performed with and without pH Control

2021 ◽  
Vol 11 (7) ◽  
pp. 2921
Author(s):  
Rosa Colucci Cante ◽  
Marianna Gallo ◽  
Federica Nigro ◽  
Francesca Passannanti ◽  
Andrea Budelli ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Growth Rate ◽  
Lactic Acid ◽  
Specific Growth Rate ◽  
Biomass Production ◽  
Acid Production ◽  
Specific Growth ◽  
Lactic Acid Production ◽  
Rice Flour ◽  
Ph Control

The mathematical modeling of fermentation processes allows for the formulation of predictions about the kinetics of biomass growth and metabolite production as well as setting or verifying the best operative conditions in view of the economical convenience of the process. For this purpose, we performed a kinetic study of a rice flour fermentation process using Lactobacillus paracasei CBA L74 with and without pH control; the pH value was set to 5.8 under pH control. Monod, Logistic, and Contois models were proposed to describe the bacterial growth rate in both conditions. The best mathematical model, which was able to describe the experimental data obtained without pH control, was the Contois model, as the specific growth rate was influenced by both the glucose reduction (from 14.31 g/L to 10.22 g/L) and the biomass production (2 log growth) that occurred during fermentation. Conversely, when pH control was implemented, both Monod and Contois models satisfactorily described the specific growth rate trend. The estimated kinetic parameters confirmed that biomass production (2 log growth) and glucose consumption (from 14.31 g/L to 6.06 g/L) did not affect the microorganism’s growth capacity when the fermenting medium was maintained at an optimal pH. The lactic acid production rate described by the Luedeking–Piret model did not appear to be linked to growth in the absence of pH control while, on the other hand, this model was unsuitable for describing the experimental lactic acid concentration when pH control was applied. The kinetic modeling of lactic acid production and the percentage of added glucose in the protocol with controlled pH will be optimized in the future.

scholarly journals Microbial Interactions between Amylolytic and Non-Amylolytic Lactic Acid Bacteria Strains Isolated during the Fermentation of Pozol

2021 ◽  
Author(s):  
Sandra Bolaños-Nuñez ◽  
Jorge A. Santiago-Urbina ◽  
Jean-Pierre Guyot ◽  
Gloria Díaz-Ruiz ◽  
Carmen Wacher
Keyword(s):  
Growth Rate ◽  
Lactic Acid ◽  
Specific Growth Rate ◽  
Kinetic Parameters ◽  
Acid Production ◽  
Specific Growth ◽  
Lactic Acid Production ◽  
Amylolytic Activity ◽  
Specific Rate ◽  
Acid Yield

Pozol is a Mexican beverage prepared from fermented nixtamalized maize dough. To contribute to understanding its complex microbial ecology, the effect of inoculating on MRS-starch pure and mixed cultures of amylolytic Sii-25124 and non-amylolytic W. confusa 17, isolated from pozol, were studied on their interactions and fermentation parameters. These were compared with L. plantarum A6, an amylolytic strain isolated from cassava. Microbial growth, kinetic parameters, amylolytic activity, lactic acid production, and hydrolysis products from starch fermentation were measured. The population dynamics were followed by qPCR. L. plantarum A6 showed higher enzymatic activity, lactic acid, biomass production, and kinetic parameters than pozol LAB in pure cultures. Mixed culture of each pozol LAB with L. plantarum A6 showed a significant decrease in amylolytic activity, lactic acid yield, specific growth rate, and specific rate of amylase production. The interaction between Sii-25124 and W. confusa 17 increased the global maximum specific growth rate (&micro;), the lactic acid yield from starch (Ylac/s), lactic acid yield from biomass (Ylac/x), and specific rate of lactic acid production (qlac) by 15, 30, 30, and 40%, respectively compared with the pure culture of Sii-25124. Interactions between the two strains are essential for this fermentation.

The effect of specific growth rate on protein synthesis and secretion in the filamentous fungus Trichoderma reesei

Microbiology ◽  
2005 ◽  
Vol 151 (1) ◽  
pp. 135-143 ◽  
Author(s):  
Tiina M. Pakula ◽  
Katri Salonen ◽  
Jaana Uusitalo ◽  
Merja Penttilä
Keyword(s):  
Growth Rate ◽  
Protein Synthesis ◽  
Specific Growth Rate ◽  
Trichoderma Reesei ◽  
Growth Rates ◽  
Protein Production ◽  
Specific Growth ◽  
Synthesis Rate ◽  
Specific Rate ◽  
Specific Growth Rates

Trichoderma reesei was cultivated in chemostat cultures on lactose-containing medium. The cultures were characterized for growth, consumption of the carbon source and protein production. Secreted proteins were produced most efficiently at low specific growth rates, 0·022–0·033 h−1, the highest specific rate of total protein production being 4·1 mg g−1 h−1 at the specific growth rate 0·031 h−1. At low specific growth rates, up to 29 % of the proteins produced were extracellular, in comparison to only 6–8 % at high specific growth rates, 0·045–0·066 h−1. To analyse protein synthesis and secretion in more detail, metabolic labelling of proteins was applied to analyse production of the major secreted protein, cellobiohydrolase I (CBHI, Cel7A). Intracellular and extracellular labelled CBHI was quantified and analysed for pI isoforms in two-dimensional gels, and the synthesis and secretion rates of the molecule were determined. Both the specific rates of CBHI synthesis and secretion were highest at low specific growth rates, the optimum being at 0·031 h−1. However, at low specific growth rates the secretion rate/synthesis rate ratio was significantly lower than that at high specific growth rates, indicating that at low growth rates the capacity of cells to transport the protein becomes limiting. In accordance with the high level of protein production and limitation in the secretory capacity, the transcript levels of the unfolded protein response (UPR) target genes pdi1 and bip1 as well as the gene encoding the UPR transcription factor hac1 were induced.

scholarly journals KINETIC EVALUATION OF ETHANOL-TOLERANT THERMOPHILE Geobacillus thermoglucosidasius M10EXG FOR ETHANOL PRODUCTION

2016 ◽  
Vol 10 (1) ◽  
pp. 24
Author(s):  
Eny Ida Riyanti ◽  
Peter L. Rogers
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Ethanol Production ◽  
Yeast Extract ◽  
Biomass Yield ◽  
Specific Growth ◽  
Kinetic Evaluation ◽  
Geobacillus Thermoglucosidasius ◽  
Low Level ◽  
Wide Range

Thermophiles are challenging to be studied for ethanol production using agricultural waste containing lignocellulosic materials rich in hexose and pentose. These bacteria have many advantages such as utilizing a wide range of substrates, including pentose (C5) and hexose (C6). In ethanol production, it is important to use ethanol tolerant strain capable in converting lignocellulosic hydrolysate. This study was aimed to investigate the growth profile of ethanol-tolerant thermophile Geobacillus thermoglucosidasius M10EXG using a defined growth medium consisted of single carbon glucose (TGTV), xylose (TXTV), and a mixture of glucose and xylose (TGXTV), together with the effect of yeast extract addition<br />to the media. The experiments were conducted at the School of Biotechnology and Biomolecular Sciences of The University of New South Wales, Australia on a shake flask fermentation at 60°C in duplicate experiment. Cultures were sampled every two hours and analised for their kinetic parameters including the maximum specific growth rate (µmax), biomass yield (Yx/s), ethanol and by-product yields (acetate and L-lactate) (Yp/s), and the doubling time (Td). Results showed that this strain was capable of growing on minimal medium containing glucose or xylose as a single carbon source. This strain utilized glucose and xylose simultaneously (co-fermentation), although there was glucose repression of xylose at relatively low glucose concentration (0.5% w/v), particularly when yeast extract (0.2% w/v) was added to the medium. The highest biomass yield was obtained at 0.5 g l-1 on glucose medium; the yield increased when yeast extract was added (at 0.59 g l-1). The highest specific growth rate of 0.25 was obtained in the phase I growth when the strain was grown on a mixture of glucose and xylose (0.5% : 0.5% w/v) medium. Diauxic growth was shown on the mixture of glucose, xylose, and yeast extract. The strain produced low level of ethanol (0.1 g l-1), as well as low level (0.2 g l-1) of by-products (L-lactate and acetate) after 15 hours. The results suggests its potential application for fermenting lignocellulosic agricultural wastes for ethanol production.

Examining the influence of substrates and temperature on maximum specific growth rate of denitrifiers

2006 ◽  
Vol 54 (8) ◽  
pp. 155-162 ◽  
Author(s):  
Y. Mokhayeri ◽  
A. Nichols ◽  
S. Murthy ◽  
R. Riffat ◽  
P. Dold ◽  
...  
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Growth Rates ◽  
Specific Growth ◽  
Treatment Plant ◽  
Capacity Utilization ◽  
Maximum Specific Growth Rate ◽  
Corn Syrup ◽  
Plant Uses ◽  
Specific Growth Rates

Facilities across North America are designing plants to meet stringent limits of technology (LOT) treatment for nitrogen removal (3–5 mg/L total effluent nitrogen). The anoxic capacity requirements for meeting LOT treatment are dependent on the growth rates of the denitrifying organisms. The Blue Plains Advanced Wastewater Treatment Plant (AWTP) is one of many facilities in the Chesapeake Bay region that is evaluating its ability to meet LOT treatment capability. The plant uses methanol as an external carbon source in a post-denitrification process. The process is very sensitive to denitrification in the winter. One approach to improve anoxic capacity utilization is to use an alternative substrate for denitrification in the winter to promote the growth of organisms that denitrify at higher rates. The aim of this study was to evaluate denitrification maximum specific growth rates for three substrates, acetate, corn syrup and methanol, at two temperatures (13 °C and 19 °C). These temperatures approximately reflect the minimum monthly and average annual wastewater temperature at the Blue Plains AWTP. The results suggest that the maximum specific growth rate (μmax) for corn syrup (1.3 d−1) and acetate (1.2 d−1) are higher than that for methanol (0.5 d−1) at low temperature of 13 °C. A similar trend was observed at 19 °C.

scholarly journals Influence of the size and form of Artemia sp. nauplii on the growth and survival of Atlantic sturgeon (Acipenser oxyrinchus Mitchill) larvae

2021 ◽  
Vol 29 (2) ◽  
pp. 69-79
Author(s):  
Iwona Piotrowska ◽  
Bożena Szczepkowska ◽  
Michał Kozłowski
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Survival Rate ◽  
Specific Growth Rate ◽  
Growth Rates ◽  
Specific Growth ◽  
Survival Rates ◽  
Atlantic Sturgeon ◽  
Growth And Survival ◽  
Acipenser Oxyrinchus

Abstract The aim of the study was to determine the influence of the size and form of Artemia sp. feed on the rearing indices of Atlantic sturgeon larvae. In the experiment, the nauplius sizes used were 480 µm (group AD), 430 µm (group AM), and 430 µm frozen nauplii (group AI). After three weeks of rearing, the sturgeon from group AD had the highest mean body weight of 0.131 g that was statistically significantly different from groups AM (0.071 g) and AI (0.033 g). The longest total length was noted in group AD (2.8 cm) and was statistically different from the others (P ≤ 0.05). Specific growth rate in groups AD and AM was 14.7 and 11.8% d−1, respectively, and these values differed statistically from those in group AI at 7.8% d−1. The highest survival rate was recorded in group AD at 60.6%, while the lowest was noted in group AI at 15.6%, and the differences between these two groups were statistically significant. The results of the experiment indicated that a feed of live 480 µm Artemia sp. nauplius significantly accelerated the growth rates and increased the survival rates of Atlantic sturgeon larvae.

The Growth of Brown trout (Salmo Trutta Linn.)

1946 ◽  
Vol 22 (3-4) ◽  
pp. 118-129
Author(s):  
MARGARET E. BROWN
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Growth Rates ◽  
Salmo Trutta ◽  
Specific Growth ◽  
Specific Rate ◽  
Size Hierarchy ◽  
Living Space ◽  
Brown Trout Salmo Trutta ◽  
Specific Growth Rates

1. Groups of trout fry of the same parentage were grown in environments where the following factors were controlled: temperature, amount and intensity of illumination, rate of water flow, aeration and chemical composition of the water, amount of living space and quality of food supply. They were allowed to eat as much as they would, and individual weights were recorded during the first 8 months after the beginning of feeding. 2. There was soon an increase in the range of individual weight in each group of fry, and thereafter the larger fry grew faster than smaller ones. When the larger fry were removed, the smaller ones grew at an increased specific rate, and when larger fry were added, the smaller ones grew more slowly. It is suggested that a ‘size hierarchy’ was established within each group, and an individual's specific growth rate depended on its position in the order of decreasing weight. 3. There was an optimum degree of crowding for maximum productivity. Compared with the fry in this group, the specific growth rates of individuals in larger, more crowded groups depended on the number of fish of larger size, while in smaller, less crowded groups, individuals grew at rates depending on the proportion of fish which were larger and smaller. 4. Alevin weight had little effect on the specific growth rates of fry. 5. There were differences between the growth histories of fry derived from alevins of the same weight and descended from the same father but different mothers (all of the same stock, age and size). 6. The specific growth rates decreased as the fry grew older, but there was no correlation between body weight and specific growth rate, except for the size hierarchy effect within each group. This effect had a greater influence on the size of individual fry than had either alevin weight or heredity.

scholarly journals Transcriptomic Insights into the Physiology of Aspergillus niger Approaching a Specific Growth Rate of Zero

2010 ◽  
Vol 76 (16) ◽  
pp. 5344-5355 ◽  
Author(s):  
Thomas R. Jørgensen ◽  
Benjamin M. Nitsche ◽  
Gerda E. Lamers ◽  
Mark Arentshorst ◽  
Cees A. van den Hondel ◽  
...  
Keyword(s):  
Growth Rate ◽  
Aspergillus Niger ◽  
Specific Growth Rate ◽  
Secondary Metabolism ◽  
Filamentous Fungi ◽  
Growth Rates ◽  
Specific Growth ◽  
Product Formation ◽  
Transcriptomic Analysis ◽  
Genes Encoding

ABSTRACT The physiology of filamentous fungi at growth rates approaching zero has been subject to limited study and exploitation. With the aim of uncoupling product formation from growth, we have revisited and improved the retentostat cultivation method for Aspergillus niger. A new retention device was designed allowing reliable and nearly complete cell retention even at high flow rates. Transcriptomic analysis was used to explore the potential for product formation at very low specific growth rates. The carbon- and energy-limited retentostat cultures were highly reproducible. While the specific growth rate approached zero (<0.005 h−1), the growth yield stabilized at a minimum (0.20 g of dry weight per g of maltose). The severe limitation led to asexual differentiation, and the supplied substrate was used for spore formation and secondary metabolism. Three physiologically distinct phases of the retentostat cultures were subjected to genome-wide transcriptomic analysis. The severe substrate limitation and sporulation were clearly reflected in the transcriptome. The transition from vegetative to reproductive growth was characterized by downregulation of genes encoding secreted substrate hydrolases and cell cycle genes and upregulation of many genes encoding secreted small cysteine-rich proteins and secondary metabolism genes. Transcription of known secretory pathway genes suggests that A. niger becomes adapted to secretion of small cysteine-rich proteins. The perspective is that A. niger cultures as they approach a zero growth rate can be used as a cell factory for production of secondary metabolites and cysteine-rich proteins. We propose that the improved retentostat method can be used in fundamental studies of differentiation and is applicable to filamentous fungi in general.

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