Repeated Batch Fermentation Process Research Articles

Kinetic modeling, sensitivity analysis, and techno-economic feasibility of ethanol fermentation from non-sterile carob extract-based media in Saccharomyces cerevisiae biofilm reactor under a repeated-batch fermentation process

This study aimed to model kinetically ethanol fermentation by Saccharomyces cerevisiae in the biofilm reactor, analyze the sensitivity of the developed model, and determine the techno-economic feasibility of ethanol fermentation. Two different media including the non-sterile enriched (NSE) and non-sterile unenriched media (NSUE) were evaluated for ethanol production. Based on the results, the experimental biomass production, ethanol production, and substrate consumption data from both the NSE and NSUE media were fitted very well by the logistic, Luedeking-Piret, and modified Luedeking-Piret models developed for each fermentation with higher R2 values than 0.96. Besides, it was determined that the ethanol production processes were growth-associated as α values (g ethanol/g substrate) were higher than β values (g ethanol/g substrate/h). Sensitivity analysis gave extremely satisfactory results with high R2 values ranging from 0.960 to 0.995. According to the techno-economic analysis, ethanol production from the NSUE medium was more economical than that of the NSE medium since its economic yield and economic productivity values were 21.0–21.1 and 13.4–16.8 times higher, respectively. Consequently, the developed models estimated successfully the experimental data yielded from non-sterile (un)enriched media in the biofilm reactor and can be used to describe ethanol fermentation under non-sterile conditions.

Isolation, identification, and application of lactic acid-producing bacteria using salted cheese whey substrate and immobilized cells technology

BackgroundLactic acid bacteria (LAB) could be used for bio-production of lactic acid (LA) from wastes of dairy industries. This study aimed to produce LA using isolated and identified LAB capable of withstanding high salt concentration of salted cheese whey and adopting immobilization technique in repeated batch fermentation process. ResultsSeventy four isolates of LAB were isolated from salted cheese whey and examined for lactic acid production. The superior isolates were biochemically and molecularly identified as Enterococcus faecalis, Enterococcus faecium, and Enterococcus hirae. Then the best of them, Enterococcus faecalis, Enterococcus hirae and dual of them besides Lacticaseibacillus casei were immobilized by sodium alginate 2% in entrapped cells. Repeated batch fermentation was executed for LA production from the mixture of salted whey and whey permeate (1:1) using immobilized strains during static state fermentation under optimum conditions (4% inoculum size in mixture contained 5% sucrose and 0.5% calcium carbonate and incubation at 37 °C). The potent bacterial strain was Enterococcus faecalis which gave the maximum LA production of 36.95 g/l with a yield of 81% after 36 h incubation at 37 °C in presence of 5% sugar. ConclusionImmobilized cells exhibited good mechanical strength during repetitive fermentations and could be used in repetitive batch cultures for more than 126 days.

Preparation of Komagataeibacter xylinus Inoculum for Bacterial Cellulose Biosynthesis Using Magnetically Assisted External-Loop Airlift Bioreactor.

The aim of this study was to demonstrate the applicability of a novel magnetically assisted external-loop airlift bioreactor (EL-ALB), equipped with rotating magnetic field (RMF) generators for the preparation of Komagataeibacter xylinus inoculum during three-cycle repeated fed-batch cultures, further used for bacterial cellulose (BC) production. The fermentation carried out in the RMF-assisted EL-ALB allowed to obtain an inoculum of more than 200× higher cellular density compared to classical methods of inoculum preparation. The inoculum obtained in the RMF-assisted EL-ALB was characterized by a high and stable metabolic activity during repeated batch fermentation process. The application of the RMF-assisted EL-ALB for K. xylinus inoculum production did not induce the formation of cellulose-deficient mutants. It was also confirmed that the ability of K. xylinus to produce BC was at the same level (7.26 g/L of dry mass), regardless of inoculum age. Additionally, the BC obtained from the inoculum produced in the RMF-assisted EL-ALB was characterized by reproducible water-related properties, mechanical strength, nano-fibrillar structure and total crystallinity index. The lack of any negative impact of inoculum preparation method using RMF-assisted EL-ALB on BC properties is of paramount value for its future applications, including use as a biomaterial in tissue engineering, wound healing, and drug delivery, where especially BC liquid capacity, nanostructure, crystallinity, and mechanical properties play essential roles.

Development of dissolved carbon dioxide‐driven‐and‐controlled repeated batch fermentation process for ethanol production

AbstractWe previously observed that as glucose is completely exhausted during ethanol fermentation, the dissolved carbon dioxide (DCO2) level in the fermenter will suddenly decline. This observation was implemented to design and develop a DCO2‐driven‐and‐controlled repeated batch fermentation process for ethanol production. The process was tested at four different glucose concentrations (~150 g/L, ~200 g/L, ~250 g/L, and ~300 g/L), and each glucose concentration was controlled under three respective DCO2 control levels (without DCO2 control, and DCO2 controlled at either 1000 mg/L or 750 mg/L). The results show that reported process features complete glucose utilization and is self‐driven. For glucose concentration less than 200 g/L, ~41%‐50% of fermentation time per batch was saved during the repeated batch operation. It took 12.1 ± 1.1 hours‐14.9 ± 1.9 hours to complete a batch with glucose feed at ~250 g/L and 21.7 ± 6 hours‐31.5 ± 7 hours to complete a batch with glucose feed at ~300 g/L. The reported process is time saving and stable, but the ethanol yield is ~20% lower than the operation without DCO2 control. Dissolved CO2 control became essential for glucose concentrations greater than 250 g/L if zero glucose discharge in each batch during the operation is desired.

Repeated-batch fermentation by immobilization of Clostridium beijerinckii NCIMB 8052 in a fibrous bed bioreactor for ABE (acetone-butanol-ethanol) production

In this study, a fibrous bed bioreactor (FBB) system was used to produce ABE (acetone-butanol-ethanol) by immobilized cells of Clostridium beijerinckii NCIMB 8052. To obtain the maximum ABE productivity and yield and maintain the stability of a repeated-batch fermentation process in the FBB system, the optimal dilution rate (0.17 min−1) and initial glucose concentration (18 g/l) in the bioreactor were determined. When the repeated-batch fermentation was maintained at 11 cycles under the optimal conditions, an average of 4.9 g/l butanol (maximum 5.3 g/l) was achieved with an average solvent productivity of 1.0 g/l/h and a yield of 0.41 g/g (maxima of 1.1 g/l/h and 0.43 g/g, respectively). However, the solvent productivity and yield in batch fermentation of free cells were just 0.29 g/l/h and 0.36 g/g, respectively. In addition, scanning electron micrographs demonstrated that C. beijerinckii cells can be adsorbed onto a cotton towel and they exhibited a significantly different morphology compared to immobilized Clostridium acetobutylicum.

Metabolic profiles analysis of 1,3‐propanediol production process by Clostridium butyricum through repeated batch fermentation coupled with activated carbon adsorption

1,3-propanediol production by Clostridium butyricum is a low productivity process due to the long time seed cultivation and thus hinders its industrial scale production. In the present study, repeated batch fermentation coupled with activated carbon adsorption strategy was first established which conduced not only to saving the time of seed cultivation and enhancing the productivity, but also to reducing the costs for the seed cultivation to achieve the purpose of 1,3-propanediol continuous production. The concentration of 1,3-propanediol from first to fourth cycle was 42.89, 45.78, 44.48, 42.39 (g/L), and the corresponding volumetric productivity was 2.14, 1.91, 1.85, 2.12 (g/L · h-1 ) respectively. More importantly, a relatively complete schematic diagram of the proposed metabolic pathways was firstly mapped out based on the intracellular metabolites analysis through GC-MS. At the same time, metabolic pathway and principal components analyses were carried out to give us deep insight into metabolic state. Many metabolites occurred to response to the stress in Cycle II. Even resting body formed and lipid accumulated owing to the worsening environment in the group without activated carbon in Cycle III. Thus, it demonstrated that activated carbon provided a favorable microenvironment for Clostridium butyricum in the repeated batch fermentation process to achieve the purpose of 1,3-propanediol continuous production.

Production of a potential liquid plant bio-stimulant by immobilized Piriformospora indica in repeated-batch fermentation process

Piriformospora indica, a mycorrhizal-like fungus able to establish associations with roots of a wide range of plants, supporting plant nutrition and increasing plant resistance and tolerance to stress, was shown to solubilise phosphate applied in the form of animal bone char (HABO) in fermentation systems. The process of P solubilisation was caused most likely by proton extrusion and medium pH lowering. The fungal mycelium was successfully immobilized/retained in a polyurethane foam carrier. Further employment of the immobilized mycelium in repeated-batch fermentation process resulted in at least 5 cycles of P solubilization. The concentration of soluble P increased during the experiment with 1.0 and 3.0 g HABO l−1 and at the end of the 5th batch cycle reached 40.8 and 120 mg l−1, respectively. The resulting final liquid product, without or with solubilized phosphate, was found to significantly increase plant growth and P plant uptake. It can be used as a biostimulant containing microbial plant growth-promoting substances and soluble P derived from renewable sources (HABO) thus supporting the development of sustainable agro-ecosystems.

Repeated-batch fermentation of L-lactic acid from acid hydrolysate of sweet sorghum juice using mixed neutralizing agent under unsterilized conditions

BACKGROUND Efficient bioconversion of biomass-derived sugars and a mild process under unsterile conditions are key challenges for an economically and sustainably feasible process for L-lactic acid fermentation. The open repeated-batch fermentation of L-lactic acid from sweet sorghum juice using mixed neutralizing agent is reported for the first time. RESULTS With the optimized mode of neutralizing agent addition (60 g L−1 sodium lactate and 40 g L−1 calcium lactate) and acid hydrolysate of sweet sorghum juice and yeast extract and salts medium, the L-lactic acid titer, yield and productivity reached 102 g L−1, 0.942 g g−1 and 2.90 g L−1 h−1, respectively. Furthermore, corn steep powder substituting yeast extract and salts proved to be an efficient supplement to acid hydrolysate of sweet sorghum juice in this process. CONCLUSION Based on sweet sorghum juice, an open repeated-batch fermentation process of L-lactic acid using mixed neutralizing agent was developted. The good stability in long-term operation over five batch fermentations indicates an efficient way of L-lactic acid production from sweet sorghum juice. © 2017 Society of Chemical Industry

Bioconversion of tea polyphenols to bioactive theabrownins by Aspergillus fumigatus.

Theabrownins (TB) are water-soluble phenolic compounds associated with the various health benefits of Pu-erh tea, a post-fermented Chinese dark tea. This work reports on the production of theabrownins from infusions of sun-dried green tea leaves using a pure culture of Aspergillus fumigatus isolated from a solid-state Pu-erh tea fermentation. A theabrownins yield of 158gkg(-1) sun-dried green tea leaves was obtained in 6days at 45°C in an aerobic fermentation. In a 2l fermenter, the yield of theabrownins was 151gkg(-1) sun-dried green tea leaves in 48h of aerobic culture (45°C, 1 vvm aeration rate, 250rpm agitation speed). Extracellular polyphenol oxidase and peroxidase of A. fumigatus contributed to this bioconversion. Repeated batch fermentation process was used for producing theabrownins but was less productive than the batch process.

Dynamics of hydrogen-producing bacteria in a repeated batch fermentation process using lake sediment as inoculum

In this study, we evaluated the effectiveness of lake sediment as inoculum for hydrogen production through dark fermentation in a repeated batch process. In addition, we investigated the effect of heat treatment, applied to enrich hydrogen-producing bacteria, on the bacterial composition and metabolism. Denaturing gradient gel electrophoresis and molecular cloning, both performed using the 16S rDNA gene as target gene, were used to monitor the structure of the bacterial community. Hydrogen production and bacterial metabolism were analysed via gas chromatography and high-performance liquid chromatography. Both treated and non-treated inocula were able to produce high amounts of hydrogen. However, statistical analysis showed a clear difference in their bacterial composition and metabolism. The heat treatment favoured the growth of different Clostridia sp., in particular of Clostridium bifermentans, allowing the production of a constant amount of hydrogen over prolonged time. These cultures showed both butyrate and ethanol fermentation types. Absence of heat treatment allowed species belonging to the genera Bacillus, Sporolactobacillus and Massilia to outgrow Clostridia sp. with a reduction in hydrogen production and a significant metabolic change. Our data indicate that lake sediment harbours bacteria that can efficiently produce hydrogen over prolonged fermentation time. Moreover, we could show that the heat treatment stabilizes the bacterial community composition and the hydrogen production.

Investigation of vinegar production using a novel shaken repeated batch culture system

Nowadays, bioprocesses are developed or optimized on small scale. Also, vinegar industry is motivated to reinvestigate the established repeated batch fermentation process. As yet, there is no small-scale culture system for optimizing fermentation conditions for repeated batch bioprocesses. Thus, the aim of this study is to propose a new shaken culture system for parallel repeated batch vinegar fermentation. A new operation mode - the flushing repeated batch - was developed. Parallel repeated batch vinegar production could be established in shaken overflow vessels in a completely automated operation with only one pump per vessel. This flushing repeated batch was first theoretically investigated and then empirically tested. The ethanol concentration was online monitored during repeated batch fermentation by semiconductor gas sensors. It was shown that the switch from one ethanol substrate quality to different ethanol substrate qualities resulted in prolonged lag phases and durations of the first batches. In the subsequent batches the length of the fermentations decreased considerably. This decrease in the respective lag phases indicates an adaptation of the acetic acid bacteria mixed culture to the specific ethanol substrate quality. Consequently, flushing repeated batch fermentations on small scale are valuable for screening fermentation conditions and, thereby, improving industrial-scale bioprocesses such as vinegar production in terms of process robustness, stability, and productivity.

Evaluation for Rock Phosphate Solubilization in Fermentation and Soil–Plant System Using A Stress-Tolerant Phosphate-Solubilizing Aspergillus niger WHAK1

A strain WHAK1, identified as Aspergillus niger, was isolated from Yichang phosphate mines in Hubei province of China. The fungus developed a phosphate solubilization zone on modified National Botanical Research Institute's phosphate growth (NBRIP) agar medium, supplemented with tricalcium phosphate. The fungus was applied in a repeated-batch fermentation process in order to test its effect on solubilization of rock phosphate (RP). The results showed that A. niger WHAK1 could effectively solubilize RP in NBRIP liquid medium and released soluble phosphate in the broth, which can be illustrated by the observation of scanning electron microscope, energy-dispersive X-ray microanalysis, and Fourier transform infrared spectroscopy. Acidification of the broth seemed to be the major mechanism for RP solubilization by the fungus. Indeed, multiple organic acids (mainly gluconic acid) were detected in the broth by high-performance liquid chromatography analysis. These organic acids caused a significant drop of pH and an obvious rise of titratable acidity in the broth. The fungus also exhibited high levels of tolerance against temperature, pH, salinity, and desiccation stresses, although a significant decline in the fungal growth and release of soluble phosphate was marked under increasing intensity of stress parameters. Further, the fungus was introduced into the soil supplemented with RP to analyze its effect on plant growth and phosphate uptake of wheat plants. The result revealed that inoculation of A. niger WHAK1 significantly increased the growth and phosphate uptake of wheat plants in the RP-amended soil compared to the control soil.

The evaluation of free and encapsulated Aspergillus awamori for phosphate solubilization in fermentation and soil–plant system

Aspergillus awamori S19, a phosphate solubilizing filamentous fungi, was immobilized in Ca-alginate and agar. The immobilized microbial cells were applied in a repeated-batch fermentation process in order to test their effect on solubilization of Udaipur rock phosphate (URP) and tricalcium phosphate (TCP). Agar entrapped cells produced 106 mg l −1 whereas Ca-alginate entrapped cells produced 93 mg l −1 soluble P that was significantly higher than freely suspended cells with URP. In the presence of TCP, immobilized cells showed significantly better phosphate solubilization than free cells, viz. 340 and 345 mg l −1 in agar and Ca-alginate entrapment, respectively versus merely 291 mg l −1 with free cells. Further the immobilized cells were introduced into the soil supplemented with TCP and URP to analyze their effect on plant growth and P uptake of mung bean plants. The result showed significantly higher plant growth in the presence of fungal inoculates.

Performance of Ca-alginate immobilization support in repeated batch fermentation process for xylitol production using fluidized bed reactor

Performance of Ca-alginate immobilization support in repeated batch fermentation process for xylitol production using fluidized bed reactor

Citric acid production from glucose by yeast Candida oleophila ATCC 20177 under batch, continuous and repeated batch cultivation

The effect of air saturation on citric acid production in batch, repeated batch and chemostat cultures has been studied. It was shown that, under continuous fermentation (chemostat mode), the highest concentration of citric acid equal of 98 g/l was produced at 20% of air saturation. In contrary to continuous fermentation, displaying an optimum at 20%, 80% air saturation yielded higher values in repeated batch fermentation process. 167 g/l citric acid were produced continuously with the fill and drain technique at 4.85 days, at 80% air saturation, compared with 157.6 g/l achieved within 5.4 days at 20%. Under repeated batch fermentation, the formation rate of the generic product (Rj) as well as the specific citric acid productivity (m p ) reached a maximum of 1.283 g/(l x hr) at 4.01 days and of 0.0375 g/(g x hr) at 4.58 days, respectively. The glucose consumption rate (Rx) reached a maximum value of 3.33 g/(l x hr) entering stationary phase after 2.56 days at a glucose concentration of 131.2 g/l.

Sugar Beet Juice Fermentation byZymomonas mobilis Attached to Stainless Steel Wire Spheres

The fermentation of sugar beet juice as well as juice syrup medium by Zymomonas mobilis inoculum attached to stainless steel wire spheres was investigated. A semi-synthetic sucrose medium enriched with mineral salts and yeast extract was used as the control. It was established that raw sugar beet juice ensured good Zymomonas mobilis culture growth and slightly decreased ethanol synthesis applying both flame-burned and TiCl4-treated wire spheres as carriers (Qx = 0.05—0.06 g/l × h; Qeth = 1.02—1.22 g/l × h). High ethanol yield was also observed in juice medium (Y = 0.45-0.46 g/g), however, levan synthesis with this medium decreased. The application of juice syrup brought about less growth effect and ethanol synthesis as compared to juice medium. The use of semi-synthetic sucrose medium resulted in high levan production (Qlev = 0.6—0.7 g/l × h), however, reduced ethanol production by 40%. In conclusion, sugar beet juice or syrup is recommendable for the preparation of Zymomonas mobilis inoculum. The levan production stage has to be realized using an optimized semi-synthetic sucrose medium. The installed wire spheres filled with inocula provided the possibility for a repeated batch fermentation process, which could be recommended for both juice and semi-synthetic sucrose medium fermentation.

Fertilizing effect of microbially treated olive mill wastewater on Trifolium plants

Olive mill wastewater (OMW) with added N and Mg was used as a medium in a shake-flask, repeated-batch fermentation process with a passively immobilized, acid-producing, strain of Aspergillus niger. The latter was able to reduce the phenolic content of the waste material to 59% of its initial amount and to lower the pH of the medium. Rock phosphate, added to the OMW medium was solubilized to a maximum amount of 0·5 g/l during the fourth batch cycle with a corresponding productivity of 10·6 mg P/l.h. Five types of OMW ± RP, microbially treated or not, were tested in a soil- Trifolium system for their fertilizing ability. The beneficial effect of microbially treated OMW was more evident during the first crop cycle. The best plant growth response and P uptake were found in mycorrhizal plants grown in soil amended with fungal treated OMW+RP.

Rock phosphate solubilization by immobilized cells of Enterobacter sp. in fermentation and soil conditions

An Enterobacter sp., a phosphate-solubilizing bacterium, was immobilized in agar. Various amounts of the immobilized bioparticles were applied in a repeated-batch fermentation process in order to solubilize Venezuelan rock phosphate. A total production of 388 mg and 403 mg soluble P/l was obtained for 2.0 g rock phosphate/l in flasks containing 10 ml and 20 ml agar beads, respectively, that was significantly higher compared to a free-cell single-batch control. Whole and destroyed immobilized bioparticles were introduced into a soil enriched with rock phosphate to improve the growth of onion plants. Compared to the control supplemented with a free-cell bacterial suspension, the results showed at least equal plant growth of 80 mg/pot and shoot P concentration of 82 μg/plant when 10 destroyed beads were applied per pot.

New alcohol resistant strains of Saccharomyces cerevisiae species for potable alcohol production using molasse.

Two alcohol resistant strains of Saccharomyces cerevisiae species were isolated from a Greek vineyard plantation. The strain AXAZ-1 gave a concentration of 17.6% v/v alcohol and AXAZ-2 16.5%, when musts from raisin and sultana grapes, respectively, were employed in alcoholic fermentations. They were found to be more alcohol tolerant and fermentative in the fermentation of molasse than the traditional baker's yeast. Specifically, using an initial [symbol: see text] Be density of 16 [symbol: see text] Be at the repeated batch fermentation process, in the first as well as fourth batch, the better AXAZ-1 gave final [symbol: see text] Be densities of 6.0 and 10.5 respectively, and the baker's yeast 11.6 and 14.5.

Repeated-batch fermentation process using a thermotolerant flocculating yeast constructed by protoplast fusion

Abstract A thermotolerant flocculating yeast, Saccharomyces cerevisiae KF-7 (KF-7), was constructed by protoplast fusion of the flocculating yeast S. cerevisiae IR-2 (IR-2) and the thermotolerant yeast S. cerevisiae EP-1 (EP-1). In repeated-batch fermentation with KF-7 at 30°C in a molasses medium containing 20% (w/v) total sugar, stable fermentations could be performed continuously and an ethanol productivity of 5 g/l·h was obtained. Even at 35°C a productivity of 3.6 g/l·h was achieved, which was 1.7 times higher than that achieved with IR-2. In a flask-cultivation test, the maximum growth rate and the decay constant of KF-7 were not influenced by an increase in temperature, unlike the results for IR-2. Thus, the fusant KF-7 had acquired thermotolerance. However, KF-7 may be inferior to IR-2 in terms of osmotic tolerance.