Anaerobic Batch Fermentation Research Articles

Effects of substrate to inoculum ratio on the biochemical methane potential of piggery slaughterhouse wastes.

The aim of this study was to assess the effect of substrate to inoculum ratio (S/I ratio) on the biochemical methane potential (BMP) and anaerobic biodegradability (Ddeg) of different piggery slaughterhouse wastes, such as piggery blood, intestine residue, and digestive tract content. These wastes were sampled from a piggery slaughterhouse located in Kimje, South Korea. Cumulative methane production curves for the wastes were obtained from the anaerobic batch fermentation having different S/I ratios of 0.1, 0.5, 1.0, and 1.5. BMP and anaerobic biodegradabilities (Ddeg) of the wastes were calculated from cumulative methane production data for the tested conditions. At the lowest S/I ration of 0.1, BMPs of piggery blood, intestine residue, and digestive tract content were determined to be 0.799, 0.848, and 1.076 Nm3 kg−1-VSadded, respectively, which were above the theoretical methane potentials of 0.539, 0.644, and 0.517 Nm3 kg−1-VSadded for blood, intestine residue, and digestive tract content, respectively. However, BMPs obtained from the higher S/I ratios of 0.5, 1.0, and 1.5 were within the theoretical range for all three types of waste and were not significantly different for the different S/I ratios tested. Anaerobic biodegradabilities calculated from BMP data showed a similar tendency. These results imply that, for BMP assay in an anaerobic reactor, the S/I ratio of anaerobic reactor should be above 0.1 and the inoculum should be sufficiently stabilized to avoid further degradation during the assay.

Experiment Study on the Biogas Fermentation of the <i>Hylocereus undatus</i> Stem

In order to get the biogas fermentation potential of the Hylocereus undatus stem, this experiment was conducted the CSRT anaerobic batch fermentation with the fresh hylocereus undatus stem as the raw material and blue green algae slurry as inoculum, on the condition of feed concentration of 6.25%, temperature of 30°C and pH of 8.0. The fermentation period lasted 70 days. The results showed it produced total 4800mL biogas while went over the 90% of the biogas production in the former 48 days. The TS biogas production rate was 695mL/g, the VS biogas production rate was 80mL/g, and the raw material biogas production rate was 70mL/g. It implicated that Hylocereus undatus stem is a kind of good biogas fermentation raw material.

Study on Biogas Production by Mesophilic Fermentation with <i>Conyza canadensis</i>

In order to study in the field of fermentation to produce biogas withConyza canadensis, the anaerobic batch fermentation experiments were performed at 30°C. The results indicated that the net biogas production of the experimental group during total fermentation time of 36d was 3280ml. Further, it was calculated that the biogas production potential ofConyza canadensiswas 354ml·g-1TS or 413ml·g-1VS.

Experimental Study on Biogas Production by Mesophilic Fermentation for Rabbit Dung

In order to obtain the biogas fermentation potential of rabbit dung, the anaerobic batch fermentation experiments were performed at 30°C, the feed concentration of 6.09% and an initial pH of 7.0. The experiment was design of the control group (120mL seeding materials) and the experimental group (120mL inoculum+21.51g rabbit dung) to explore the potential of the anaerobic digestion of rabbit dung. The results show that biogas production of rabbit dung during total fermentation period of 36 days is 3084mL, TS biogas yield is 432mL/g, and gas yield is 508mL/g. The results indicated that rabbit dung can be used for biogas fermentation and the fermentation was good.

Use of G-phase for biogas production

Biogas is very promising renewable energy resource. The number of biogas plants increase every year. Currently there is a demand for new ways of organic waste treatment from production of different commodities. One of the technologies which produce waste is biodiesel production. One of the wastes from the biodiesel production is G-phase which is mainly consisted from glycerol and methanol. The aim of work was to find the effect of G-phase addition, to fermented material, on biogas resp. methane production. Two lab-scale batch anaerobic fermentation tests (hydraulic retention time 14 and 22 days) under mesophilic temperature conditions 38.5 °C have been performed. The positive effect of G-phase addition to methane production has been found. G-phase was added in three different amounts of inoculums volume 0.5 %, 1% and 1.5 %. The highest absolute methane production has been achieved by 1.5 % addition of G-phase. However it was also found difference in specific methane production due to use of different inoculum consisted of swine or cow manure. The specific methane production in hydraulic retention time of 14 days has been for the same G-phase dose 1.5 % higher for swine manure, 0.547 m3∙kg−1 of organics solids compare with cow liquid manure 0.474 m3∙kg−1 of organics solids.

Experimental Study on Energy Conversion Efficiency of Biogas Fermentation of Sorghum Distilled Residue Based on Properties of Raw Materials

In order to gain biogas production potential and energy conversion efficiency of biogas fermentation of sorghum distilled residue (SDR), the anaerobic batch fermentation experiments were performed at 30 degrees Celsius. After experiments, we got experimental results as follows: biogas production of SDR during total fermentation time of 28days is 2885mL; properties of raw materials including: TS is 88.58%, VS is 16.69%, heating value is 15.684kJ/g, TS biogas yield is 220mL/g, VS biogas yield is 1300ml/g, raw material biogas yield is 190mL/g, and energy conversion efficiency of biogas fermentation of SDR is 30.38%. The results indicate that biogas fermentation is an effective new method to recycle clean energy from SDR.

Kinetic Models of Hydrogen Production Process by Batch Anaerobic Fermentation from Contained Sugar Wastewater

The processes of biomass growth, hydrogen production and sucrose degradation were systemically investigated about batch anaerobic fermentation which is based on activated sludge for a basic strain and the simulating sucrose wastewater for a substrate. The kinetics of microbial growth, hydrogen production and sucrose degradation were proposed according to the Compertz equation and the Luedeking-Piret equation. The relationship between the biomass, hydrogen and substrate were also evaluated. The results shown that the hydrogen is a main produce of the formation process which is a growth-associated, a high biomass is favorable to increasing the hydrogen yield and shortening lag time. The three kinetic models equation have a good coincidence with the experimental data, and can really reflect the hydrogen production process from wastewater contained sucrose. The results will provide helpful reference for the large-scale production and theory study of hydrogen production.

Parameters Optimization of Two-Phase United Anaerobic Fermentation Hydrogen-Methane Production

The two-phase united anaerobic fermentation has been paid more and more attention in recent years. But how to increase the biogas production yield and the degradation rate of organic matter needs more research. The batch anaerobic fermentation studies demonstrated the feasibility of H2 and CH4 generation utilizing kitchen wastewater as substrate, and the vaccination rate, dilution rate, substrate concentration were optimized. The conclusion showed that dilution rate is the most important factor, following by kitchen wastewater concentration and inoculum volume. The most excellent program of the organic load, the inoculation volume and the dilution volume are 150 +300 ml, 135 ml, 225 ml, respectively. Under these conditions the hydrogen and methane production rate were the highest of 4.15 ml/ml，2.55 ml/ml (calculated as the wastewater volume), respectively. The acid-forming pathways of kitchen wastewater was typical butyric- propionic acid mixed fermentation type. The appropriate dilution could decrease the concentration of the total acids and increase the biogas production yield.

Comparison of Ethanol Fermentation Properties between Laboratorial and Industrial Yeast Strains using Cassava Hydrolysate

In order to investigate the ethanol fermentation properties of alcohol yeasts a laboratorial strain (CEN.PK2-1D) and two industrial alcohol yeasts (JHS100 and JHS200) of Saccharomyces cerevisiae were cultured in a pure YP medium with 300 g/L glucose and cassava hydrolysate. Spot assay and cell viability tests showed that both the JHS100 and JHS200 strains exhibited higher ethanol tolerance than the CEN.PK2-1D strain. The JHS100 strain demonstrated the highest cell growth, glucose consumption and ethanol production. In particular, an anaerobic batch fermentation of the JHS100 strain using cassava hydrolysate with 250 g/L glucose resulted in a 106.1 g/L ethanol concentration, 0.42 g/g ethanol yield and 3.15 g/L-hr ethanol productivity, which were 53%, 13%, 53% higher than the corresponding values for the CEN.PK2-1D strain. By changing the pure YP medium to cassava hydrolysate, 19% and 17% decreases in ethanol yield and productivity for the CEN.PK2-1D strain were observed, whereas the cultures of the JHS100 and JHS200 stains showed similar ethanol productivities and only an 8% decrease in ethanol yield. Furthermore, the JHS100 and JHS200 stains produced lower levels of glycerol and acetate byproducts than the CEN.PK2-1D strain. Consequently, the outstanding ethanol fermentation performance of the industrial strains might be owing to rapid cell growth, high ethanol tolerance, low nitrogen requirements and the low formation of by-products.

Effect of biotin and a similar compound on succinic acid fermentation by Actinobacillus succinogenes in a chemically defined medium

A minimal chemically defined medium (CDM) was created and used to study the effect of biotin on the metabolism of Actinobacillus succinogenes NJ 113. The medium contained four amino acids and vitamins as key growth factors. To gain insight into the effect of biotin, different concentrations of this compound were added, and glucose utilisation, cell growth, and the succinic acid concentration were investigated. Anaerobic batch fermentation was carried out at optimised conditions in a 3L fermentor with a succinic acid concentration of 45.2g/L and a yield of 90.4%. A metabolic pathway was proposed after further study of the mechanism underlying the metabolism of biotin. The same results were obtained when 5-aminolevulinate (5-ALA) was used instead of biotin. We suggest that 5-ALA is a great alternative to biotin for the preparation of succinic acid by biological fermentation.

Effect of fermentation conditions on biohydrogen production from lipid-rich food material

Among the basic components of organic materials, such as carbohydrate, protein, and lipid, the hydrogen yield of carbohydrate fermentation has been reported to be significantly higher than that of lipid. This study used lard as a model organic matter for lipid and investigated its H2 production potential in batch anaerobic fermentation experiments under various combinations of stirring and CO2-scavenging conditions. A significant increase in the hydrogen yield was observed in both CO2-scavenging and stirring conditions; the CO2-scavenging condition yield was 2.9 times higher than the stirring condition (116.7 and 40.3 mL H2/g volatile solid [VS], respectively), which was much greater than reported previously. A maximal hydrogen yield of 185.8 mL H2/g VS was obtained in the presence of both CO2-scavenging and stirring, and the H2 content of the total biogas was as high as 99% (v/v). In addition, there was less H2 and more CH4 production in the absence of CO2-scavenging and/or stirring, which suggests that the consumption of H2 and CO2 for methanogenesis was the major mechanism of the poor hydrogen yield from lipid. The volatile fatty acids in all the tests consisted primarily of valeric (47.2–54.9%) and propionic acids (26.6–30.3%), and higher concentrations of these acids remained in the fermentation liquid without CO2 removal. These results suggest that lipid-rich food waste is a potential source for H2 production if the fermentation process is optimized to minimize the partial pressure of CO2 and H2 and restrain the activities of H2-consuming bacteria.

Anaerobic Fermentation of Cow Dung and Slurry from Hydrogen Fermentation Production of Sucrose

This paper reported an experiment about anaerobic fermentation of cow dung and slurry from hydrogen fermentation production of sucrose by using anaerobic batch fermentation at temperature of 30°C, the results indicated that methane fermentation production can be achieved through this experiment with 40d anaerobic fermentation, its biogas yield is 212 ml/g TS and 239ml/g VS, fresh material biogas yield is 46 ml/g.

Dynamic metabolomics differentiates between carbon and energy starvation in recombinant Saccharomyces cerevisiae fermenting xylose

BackgroundThe concerted effects of changes in gene expression due to changes in the environment are ultimately reflected in the metabolome. Dynamics of metabolite concentrations under a certain condition can therefore give a description of the cellular state with a high degree of functional information. We used this potential to evaluate the metabolic status of two recombinant strains of Saccharomyces cerevisiae during anaerobic batch fermentation of a glucose/xylose mixture. Two isogenic strains were studied, differing only in the pathways used for xylose assimilation: the oxidoreductive pathway with xylose reductase (XR) and xylitol dehydrogenase (XDH) or the isomerization pathway with xylose isomerase (XI). The isogenic relationship between the two strains ascertains that the observed responses are a result of the particular xylose pathway and not due to unknown changes in regulatory systems. An increased understanding of the physiological state of these strains is important for further development of efficient pentose-utilizing strains for bioethanol production.ResultsUsing LC-MS/MS we determined the dynamics in the concentrations of intracellular metabolites in central carbon metabolism, nine amino acids, the purine nucleotides and redox cofactors. The general response to the transition from glucose to xylose was increased concentrations of amino acids and TCA-cycle intermediates, and decreased concentrations of sugar phosphates and redox cofactors. The two strains investigated had significantly different uptake rates of xylose which led to an enhanced response in the XI-strain. Despite the difference in xylose uptake rate, the adenylate energy charge remained high and stable around 0.8 in both strains. In contrast to the adenylate pool, large changes were observed in the guanylate pool.ConclusionsThe low uptake of xylose by the XI-strain led to several distinguished responses: depletion of key metabolites in glycolysis and NADPH, a reduced GTP/GDP ratio and accumulation of PEP and aromatic amino acids. These changes are strong indicators of carbon starvation. The XR/XDH-strain displayed few such traits. The coexistence of these traits and a stable adenylate charge indicates that xylose supplies energy to the cells but does not suppress a response similar to carbon starvation. Particular signals may play a role in the latter, of which the GTP/GMP ratio could be a candidate as it decreased significantly in both strains.

Parameter Estimation in Batch Bioreactor Simulation Using Metabolic Models: Sequential Solution with Direct Sensitivities

In this study, we propose a parameter estimation method for genome-scale dynamic flux balance (DFBA) models. A bilevel optimization problem is reformulated as a differential-algebraic equation (DAE) optimization problem and solved sequentially, using gradient-based optimization with direct sensitivity equations. The resulting solution method is computationally efficient for today’s largest genome-scale metabolic models. The parameter estimation method combined with parameter selection algorithm is applied on simulated and experimental data. This paper presents the parameter estimation and selection method and numerical results of estimation of kinetic parameters of the DFBA model of anaerobic batch fermentation. The results show improved computational performance over previous approaches, thus making parameter estimation available for genome-scale DFBA models.

A biochemically structured model for ethanol fermentation by Kluyveromyces marxianus: A batch fermentation and kinetic study

Anaerobic batch fermentations of ricotta cheese whey (i.e. containing lactose) were performed under different operating conditions. Ethanol concentrations of ca. 22 g L −1 were found from whey containing ca. 44 g L −1 lactose, which corresponded to up to 95% of the theoretical ethanol yield within 15 h. The experimental data could be explained by means of a simple knowledge-driven biochemically structured model that was built on bioenergetics principles applied to the metabolic pathways through which lactose is converted into major products. Use of the model showed that the observed concentrations of ethanol, lactose, biomass and glycerol during batch fermentation could be described within a ca. 6% deviation, as could the yield coefficients for biomass and ethanol produced on lactose. The model structure confirmed that the thermodynamics considerations on the stoichiometry of the system constrain the metabolic coefficients within a physically meaningful range thereby providing valuable and reliable insight into fermentation processes.

Improving the ethanol yield by reducing glycerol formation using cofactor regulation in Saccharomyces cerevisiae

To increase ethanol yield and decrease glycerol production in Saccharomyces cerevisiae, the strategies of direct cofactor-regulation were explored. During anaerobic batch fermentations, the yeast expressing Bacillus cereus gapN gene, encoding non-phosphorylating NADP(+)-dependent glyceraldehyde-3-phosphate dehydrognease, produced 73.8g ethanoll(-1), corresponding to 96% of theoretical maximum yield compared to 92% for the wild type. The yeast expressing Escherichia coli frdA gene encoding the NAD(+)-dependent fumarate reductase, exhibited a 22% (relative to the amount of substrate consumed) increase in glycerol yield in medium containing 2g fumaratel(-1). The yeast expressing mhpF gene, encoding acetylating NAD(+)-dependent acetaldehyde dehydrogenase, produced 74.5g ethanoll(-1), corresponding to 97.4% of theoretical maximum yield while glycerol decreased by 40% when acetic acid was added before inoculation. This strain represents a promising alternative for ethanol production with lignocellulosic hydrolysates where acetate is available at significant amounts.

Minimization of glycerol synthesis in industrial ethanol yeast without influencing its fermentation performance

To synthesize glycerol, a major by-product during anaerobic production of ethanol, the yeast Saccharomyces cerevisiae would consume up to 4% of the sugar feedstock in typical industrial ethanol processes. The present study was dedicated to decreasing the glycerol production mostly in industrial ethanol producing yeast without affecting its desirable fermentation properties including high osmotic and ethanol tolerance, natural robustness in industrial processes. In the present study, the GPD1 gene, encoding NAD +-dependent glycerol-3-phosphate dehydrogenase in an industrial ethanol producing strain of S. cerevisiae, was deleted. Simultaneously, a non-phosphorylating NADP +-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPN) from Bacillus cereus was expressed in the mutant deletion of GPD1. Although the resultant strain AG1A ( gpd1△ P PGK - gapN) exhibited a 48.7±0.3% (relative to the amount of substrate consumed) lower glycerol yield and a 7.6±0.1% (relative to the amount of substrate consumed) higher ethanol yield compared to the wild-type strain, it was sensitive to osmotic stress and failed to ferment on 25% glucose. However, when trehalose synthesis genes TPS1 and TPS2 were over-expressed in the above recombinant strain AG1A, its high osmotic stress tolerance was not only restored but also improved. In addition, this new recombinant yeast strain displayed further reduced glycerol yield, indistinguishable maximum specific growth rate ( μ max) and fermentation ability compared to the wild type in anaerobic batch fermentations. This study provides a promising strategy to improve ethanol yields by minimization of glycerol production.

Improving ethanol productivity by modification of glycolytic redox factor generation in glycerol-3-phosphate dehydrogenase mutants of an industrial ethanol yeast

The GPD2 gene, encoding NAD(+)-dependent glycerol-3-phosphate dehydrogenase in an industrial ethanol-producing strain of Saccharomyces cerevisiae, was deleted. And then, either the non-phosphorylating NADP(+)-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPN) from Bacillus cereus, or the NADP(+)-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Kluyveromyces lactis, was expressed in the obtained mutant AG2 deletion of GPD2, respectively. The resultant recombinant strain AG2A (gpd2Δ P (PGK)-gapN) exhibited a 48.70 ± 0.34% (relative to the amount of substrate consumed) decrease in glycerol production and a 7.60 ± 0.12% (relative to the amount of substrate consumed) increase in ethanol yield, while recombinant AG2B (gpd2Δ P (PGK)-GAPDH) exhibited a 52.90 ± 0.45% (relative to the amount of substrate consumed) decrease in glycerol production and a 7.34 ± 0.15% (relative to the amount of substrate consumed) increase in ethanol yield compared with the wild-type strain. More importantly, the maximum specific growth rates (μ (max)) of the recombinant AG2A and AG2B were higher than that of the mutant gpd2Δ and were indistinguishable compared with the wild-type strain in anaerobic batch fermentations. The results indicated that the redox imbalance of the mutant could be partially solved by expressing the heterologous genes.

Hydrogen production from sludge of poultry slaughterhouse wastewater treatment plant pretreated with microwave

This study aims to produce hydrogen from sludge of poultry slaughterhouse wastewater treatment plant (5% total solid) by anaerobic batch fermentation with Enterobactor aerogenes or mixed cultures from hot spring sediment as the inoculums. Sludge was heated in microwave at 850 W for 3 min. Results indicated that a soluble chemical oxygen demand (sCOD) of pretreated sludge was higher than that of raw sludge. Pretreated sludge inoculated with E. aerogenes and supplemented with the Endo nutrient had a higher hydrogen yield (12.77 mL H 2/g tCOD) than the raw sludge (0.18 mL H 2/g tCOD). When considered the hydrogen yield, the optimum initial pH for hydrogen production from microwave pretreated sludge was 5.5 giving the maximum value of 12.77 mL H 2/g tCOD. However, when considered the hydrogen production rate ( R m), the optimum pH for hydrogen production would be 9.0 with the maximum R m of 22.80 mL H 2/L sludge·h.

Optimization of ricotta cheese whey (RCW) fermentation by response surface methodology

A central composite design (CCD) was performed to evaluate the effects of four factors, i.e. temperature (T), pH, agitation rate (K) and initial lactose concentration (L), on ricotta cheese whey batch fermentation and to optimize the process leading to the formation of bio-ethanol. Anaerobic batch fermentation experiments were carried out by using the yeast Kluyveromyces marxianus. After a preliminary experimental analysis, the values of the chosen factors were 32 and 40 degrees C for T, 4 and 6 for pH, 100 and 300 rpm for K, 40 and 80 g L(-1) for L. Response surface methodology (RSM) was used to optimize the fermentation process and an empirical polynomial model was used to fit the experimental data. The best operating conditions resulted to be T=32.35 degrees C, pH 5.41, K=195.56 rpm and L=40 g L(-1) and the model ensured a good fitting of the observed data.