Feed Medium Research Articles

Optimization of self-fermented period of waste coconut endosperm destined to feed black soldier fly larvae in enhancing the lipid and protein yields

The prime objective of this study was to simultaneously enhance the lipid and protein yields from black soldier fly larvae (BSFL) fed with waste coconut endosperm. The waste coconut endosperm impoverished with nutrient content lost during milk extraction was nutritively fortified via self-fermentation process with time period ranging from 2 to 8 weeks before administering to BSFL. The results showed peak nutrient content was attained from week-4 self-fermented waste coconut endosperm. Using this feed medium, the BSFL prepupae could accumulate 58% of its biomass weight with lipid. The low polyunsaturated fatty acid (6%) and high C18:1 (50%) also guaranteed high biodiesel quality derived from BSFL. Nevertheless, the longer BSFL rearing duration when fed with week-6 self-fermented waste coconut endosperm had triggered a slight increase in protein yield (18%) in comparison with week-4 medium (15%). In considering of organic waste treatment advantage of week-4 self-fermented waste coconut endosperm, a total waste reduction of 0.019 g/d was successfully measured using only 20 BSFL. Therefore, week-4 self-fermented period was concluded as an optimum to produce ideal waste coconut endosperm feed medium for BSFL in enhancing the simultaneous lipid and protein yields.

Change of Monascus pigment metabolism and secretion in different extractive fermentation process

Monascus pigments that were generally produced intracellularly from Monascus spp. are important natural colorants in food industry. In this study, change of pigment metabolism and secretion was investigated through fed-batch extractive fermentation and continuous extractive fermentation. The biomass, secreting rate of pigment and total pigment yield closely correlated with the activated time of extractive fermentation as well as the composition of feeding nutrients. Metal ions played a key role in both the cell growth and pigment metabolism. Nitrogen source was necessary for a high productivity of biomass but not for high pigment yield. Furthermore, fermentation period for the fed-batch extractive fermentation could be reduced by 18.75% with a nitrogen source free feeding medium. Through a 30-day continuous extractive fermentation, the average daily productivity for total pigments reached 74.9AUday-1 with an increase by 32.6 and 296.3% compared to that in a 6-day conventional batch fermentation and a 16-day fed-batch extractive fermentation, respectively. At the meantime, proportions of extracellular pigments increased gradually from 2.7 to 71.3%, and yellow pigments gradually became dominated in both intracellular and extracellular pigments in the end of continuous extractive fermentation. This findings showed that either fed-batch or continuous extractive fermentation acted as a promising method in the efficient production of Monascus pigments.

An Effective Method of Continuous Production of Erythritol from Glycerol by Yarrowia lipolytica MK1.

This study demonstrates the potential applicability of the UV mutant Yarrowia lipolytica MK1 for the valorisation of glycerol and erythritol production in a chemostat culture. The aim of this research is to investigate the optimal C:N ratio in the feeding medium in order to enhance erythritol production. The highest erythritol concentration, at 113.1 g/L with a volumetric erythritol production rate of 1.1 g/(L·h) and a yield of 0.57 g/g, was obtained in the feeding medium with a C:N ratio of 80:1. Moreover, no residual glycerol was observed in the culture broth during cultivation. The chemical composition of the biomass was analysed. The contents of lysine and threonine in the biomass protein amino acid profile were higher than those required by the FAO/WHO for fodder yeast.

Experimental results of parallel connected inverters feeding medium voltage transformer

Experimental results of parallel connected inverters feeding medium voltage transformer

Analysis of compaction and life‐time prediction of porous polymer membranes: influence of morphology, diffusion and creep behaviour

AbstractIn membrane applications, large values of permeability and selectivity are generally desired during the whole period of application. The permeability of porous polymer membranes often is reduced by the effect of compaction. Compaction of polymer membranes is a time‐dependent process which is strongly determined by the viscoelastic properties of the polymer and its plasticisation caused by the feed medium (e.g. a liquid medium or a process gas in the case of porous support structures). In this study, the time‐dependent compaction of porous polymer membranes under pressure is modelled. The influence of viscoelastic and diffusion properties of the polymer material on the permeability of the membrane is analysed for different types of membrane morphologies. The life‐time of a porous polymer membrane is associated with the time at which the glass transition is achieved in a creep experiment. Equations are derived in order to estimate the maximum life‐time of polymer membranes based on compaction. The analysis reveals that the diffusion coefficient, the average retardation time in creep, the magnitude of creep compliance and the time–temperature–pressure shift factor strongly influence compaction of microporous membranes. Generally, a larger tortuosity at constant porosity yields a lower life‐time of the membrane. Buckling of cell struts is the dominant failure mechanism in porous membranes with a very high porosity and allows an estimation of life‐time. © 2016 Society of Chemical Industry

Determining putative vectors of the Bogia Coconut Syndrome phytoplasma using loop-mediated isothermal amplification of single-insect feeding media.

Phytoplasmas are insect vectored mollicutes responsible for disease in many economically important crops. Determining which insect species are vectors of a given phytoplasma is important for managing disease but is methodologically challenging because disease-free plants need to be exposed to large numbers of insects, often over many months. A relatively new method to detect likely transmission involves molecular testing for phytoplasma DNA in sucrose solution that insects have fed upon. In this study we combined this feeding medium method with a loop-mediated isothermal amplification (LAMP) assay to study 627 insect specimens of 11 Hemiptera taxa sampled from sites in Papua New Guinea affected by Bogia coconut syndrome (BCS). The LAMP assay detected phytoplasma DNA from the feeding solution and head tissue of insects from six taxa belonging to four families: Derbidae, Lophopidae, Flatidae and Ricaniidae. Two other taxa yielded positives only from the heads and the remainder tested negative. These results demonstrate the utility of combining single-insect feeding medium tests with LAMP assays to identify putative vectors that can be the subject of transmission tests and to better understand phytoplasma pathosystems.

Testing plasmid stability of Escherichia coli using the Continuously Operated Shaken BIOreactor System.

Plasmids are common vectors to genetically manipulate Escherichia coli or other microorganisms. They are easy to use and considerable experience has accumulated on their application in heterologous protein production. However, plasmids can be lost during cell growth, if no selection pressure like, e.g., antibiotics is used, hampering the production of the desired protein and endangering the economic success of a biotechnological production process. Thus, in this study the Continuously Operated Shaken BIOreactor System (COSBIOS) is applied as a tool for fast parallel testing of strain stability and operation conditions and to evaluate measures to counter such plasmid loss. In specific, by applying various ampicillin concentrations, the lowest effective ampicillin dosage is investigated to secure plasmid stability while lowering adverse ecological effects. A significant difference was found in the growth rates of plasmid-bearing and plasmid-free cells. The undesired plasmid-free cells grew 30% faster than the desired plasmid-bearing cells. During the testing of plasmid stability without antibiotics, the population fraction of plasmid-bearing cells rapidly decreased in continuous culture to zero within the first 48 h. An initial single dosage of ampicillin did not prevent plasmid loss. By contrast, a continuous application of a low dosage of 10 µg/mL ampicillin in the feed medium maintained plasmid stability in the culture. Consequently, the COSBIOS is an apt reactor system for measuring plasmid stability and evaluating methods to enhance this stability. Hence, decreased production of heterologous protein can be prevented. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1418-1425, 2016.

Spray Dried Chitosan Microparticles for Intravesical Delivery of Celecoxib: Preparation and Characterization

Chitosan microparticles containing celecoxib (CB), were developed as chemoprevention of bladder cancer. Furthermore two inclusion complexes of CB with methyl-β-cyclodextrin (C1 and C2) were prepared to improve the solubility of the drug. C1 and C2 were obtained by freeze-drying and characterized in the solid state and in solution. Microparticles loaded with CB or C1 or C2 were prepared by spray drying and fully characterized. The yield and encapsulation efficiencies of microparticles depended by both the viscosity and the presence of the inclusion complex in the feed medium nebulised. Generally, the microparticles exhibited a spherical shape with mean diameter of approximately 2μm which was compatible with local intravesical administration using a catheter. The CB release studies from the microparticles allowed us to identify both immediate release systems (microparticles including the complexes) and prolonged release systems (microparticles including CB alone). The latter exhibited good adhesion to the bladder mucosa, as highlighted by a mucoadhesion study. Histological studies revealed a desquamation of the superficial cells when the bladder mucosa was treated with microparticles loaded with CB, while the morphology of the urothelium did not change when it was treated with microparticles loaded with the inclusion complex. A new CB intravesical formulation than can easily be administered with a catheter and is able to release the drug at the target site for several hours was realized. This new delivery system could be a good alternative to classic oral CB administration.

Food Industry Waste’s Exploitation via Anaerobic Digestion and Fermentative Hydrogen Production in an Up-Flow Column Reactor

The present study focuses on the exploitation of food industry waste for hydrogen and methane production, via biological processes. Fermentative hydrogen production in an anaerobic up-flow column reactor (AUFCR), using indigenous microbial species and fed with the soluble fraction of the waste coming after an extraction procedure, was investigated at different Hydraulic Retention Times (HRTs) in the range of 12–2 h. The highest hydrogen production rate (2.94 ± 0.37 L H2/L/d) was obtained at the HRT of 2 h, while the highest yield of hydrogen produced per mol of consumed carbohydrates, expressed in glucose equivalents was achieved at the HRT of 12 h (0.14 ± 0.01 mol/mol). Methane production via anaerobic digestion (AD) in a CSTR—type reactor was also assessed, using the whole diluted food industry waste (without extraction). The HRTs tested were 20, 15 and 10 days, while when the reactor operated at the HRT of 10 days, the feeding medium was also thermally treated, in order to assess the effect of pretreatment in AD. The maximum methane production rate (0.24 ± 0.02 L CH4/L/d) was observed for the HRT of 10 days and thermally treated substrate, while the maximum methane yield was obtained at the HRT of 15 days (247.9 ± 0.15 L CH4/kg waste). The IWA ADM1 model was finally used to predict the anaerobic digesters’ behavior through the operational period, resulting to a quite satisfactory simulation for a wide range of operational conditions.

Transport and metabolism of fumaric acid in Saccharomyces cerevisiae in aerobic glucose-limited chemostat culture.

Currently, research is being focused on the industrial-scale production of fumaric acid and other relevant organic acids from renewable feedstocks via fermentation, preferably at low pH for better product recovery. However, at low pH a large fraction of the extracellular acid is present in the undissociated form, which is lipophilic and can diffuse into the cell. There have been no studies done on the impact of high extracellular concentrations of fumaric acid under aerobic conditions in S. cerevisiae, which is a relevant issue to study for industrial-scale production. In this work we studied the uptake and metabolism of fumaric acid in S. cerevisiae in glucose-limited chemostat cultures at a cultivation pH of 3.0 (pH < pK). Steady states were achieved with different extracellular levels of fumaric acid, obtained by adding different amounts of fumaric acid to the feed medium. The experiments were carried out with the wild-type S. cerevisiae CEN.PK 113-7D and an engineered S. cerevisiae ADIS 244 expressing a heterologous dicarboxylic acid transporter (DCT-02) from Aspergillus niger, to examine whether it would be capable of exporting fumaric acid. We observed that fumaric acid entered the cells most likely via passive diffusion of the undissociated form. Approximately two-thirds of the fumaric acid in the feed was metabolized together with glucose. From metabolic flux analysis, an increased ATP dissipation was observed only at high intracellular concentrations of fumarate, possibly due to the export of fumarate via an ABC transporter. The implications of our results for the industrial-scale production of fumaric acid are discussed.

Responses of CHO-DHFR cells to ratio of asparagine to glutamine in feed media: cell growth, antibody production, metabolic waste, glutamate, and energy metabolism

Optimization of chemically defined medium has been a critical way to produce monoclonal antibody. Usually, amount of glutamine was added into the feed medium, but a half of asparagine was added. Our study found that asparagine was important in the antibody production phase. Increasing the ratio of asparagine to glutamine in feed medium for enhancement of antibody production in CHO-DHFR cell culture would be an efficient way. We optimized the total amount and the ratio of the two vital amino acids in feed medium to increase antibody production. In this work, we have demonstrated that feeding medium of high ratio between asparagine and glutamine (FB-H) can enhance the cell density after reaching the stationary phase. Moreover, FB-H was shown to improve cell maintenance, and increased the antibody production. The metabolic flux analysis proved that ratio of asparagine to glutamine had little influence on glycolysis. Furthermore, the TCA cycle of FB-H was enhanced by 20 % compared to that of low ratio of asparagine to glutamine (FB-L). And the energy metabolism of FB-H was 22.6 % higher than that of FB-L. For the later, lactate can be less produced in FB-H. We should improve the ratio between asparagine and glutamine in feed medium properly under the premise of no influence on cell growth to achieve high mAb producing goal.

المشروعات الصغیرة وأثرها فی التنمیة الاقتصادیة :مصر نموذجا

يهدف هذا البحث إلى إلقاء الضوء على المشروعات الصغيرة، وبيان الآثار الاقتصادية لها على الاقتصاد، وتوضيح مدى الارتباط بين فعالية المشروعات الصغيرة وتحقيق التنمية الاقتصادية. وفي سبيل تحقيق أهداف البحث تم دراسة الوضع الراهن للمشروعات الصغيرة في مصر وذلک للوقوف على وضعها الحالي في ظل معدلات التنمية الاقتصادية، ثم دراسة الآفاق المستقبلية لهذا الدور الذي يمکن أن تلعبه هذه المشروعات مستقبلا في ظل الظروف التي انتابت معظم اقتصاديات دول العالم ومنها مصر. ومن خلال نتائج البحث أوصت الباحثة بمجموعة من التوصيات والمقترحات. أن قضية المشروعات الصغيرة والمتوسطة تحتل أهمية کبري لدي صناع القرار الاقتصادي في الدول المتقدمة والنامية على حد سواء، لما لهذه المشروعات من دور محوري في التنمية الاقتصادية والاجتماعية. وتتجسد أهميتها، في قدرتها على توليد الوظائف بمعدلات کبيرة وتکلفه رأسمالية قليلة. کما أن للمشروعات الصغيرة روابط خلفية قوية مع المشروعات المتوسطة والکبيرة، وتساهم في زيادة الدخل وتنويعه، وزيادة القيمة المضافة المحلية، کما أنها تمتاز بکفاءة استخدام رأس المال نظرا للارتباط المباشر لملکية المشروع بإدارته، وحرص المالک على نجاح مشروعه وإرادته بالطريقة المثلي. وبالرغم من أن المشروعات الصغيرة(SSE - Small Scale Enterprises) تحظى باهتمام ورعاية الدول المتقدمة والنامية، فإن منطلق الاهتمام وأسبابه تختلف في الدول المتقدمة عنها في الدول النامية، فالدول المتقدمة أدرکت أهمية هذه المشروعات لما لها من دور في تغذية المشروعات المتوسطة والکبرى بالمنتجات الوسيطية، أما في الدول النامية يأتي إهتمامها بهذا النوع من المشروعات منطلقا من إجراءات الإصلاح الإقتصادي، ولإيجاد فرص عمل للأعداد المتزايدة من الخرجين إلى سوق العمل. Small and medium enterprises occupies a significant importance with the Economic decision-makers in developed and developing countries as these projects have a pivotal role in economic and social development. And it reflected its importance, in their ability to generate jobs at high rates and low capital cost. Also, small businesses ties background with medium and large projects, and contribute to increased income and diversification, and increase local value added, as well as characterized by the efficient use of capital because of the direct correlation to the ownership and management, and the willingness of the owner of the success of his project at an optimal way. Despite the fact that small enterprises (SSE - Small Scale Enterprises) receive the attention and care of developed and developing countries, the terms of interest and its causes vary in developed countries than developing countries. Developed countries realized the importance of these projects because of their role in feeding medium and large projects intermediate products. In developing countries, interest in this kind of projects comes from a platform of economic reform measures, and to find jobs for the growing numbers of graduates into the labor market.

Highly efficient l-lactic acid production from xylose in cell recycle continuous fermentation using Enterococcus mundtii QU 25

We report an effective cell recycling continuous fermentation of xylose to l-lactic acid with high concentration, productivity, and yield using strain QU 25. pH was found to affect the yield and corn steep liquor as feeding medium enhanced the yield.

Performance Analysis of Cylindrical Grinding Process Parameters Using Grey Relational Technique&lt;sup&gt;&lt;/sup&gt;

The present research work involves investigating the cylindrical grinding process parameters of Al/SiC metal matrix composites during machining. The effect of grinding process parameters on grinding force, surface roughness and grinding temperature were investigated experimentally using L27 orthogonal array. Grinding process was carried out using different combination of wheel velocity, workpiece velocity, feed rate and depth of cut. The significant grinding process parameters have been determined by using ANOVA. The grey grades identify the optimum level grinding process parameters. From the grey relational grade, low wheel velocity, medium workpiece velocity, medium feed rate and medium depth of cut gives the best results.

Development of Fed-Batch Cultivation Strategy for Efficient Oxytetracycline Production by Streptomyces rimosus at Semi-Industrial Scale

Oxytetracycline (OTC) production byStreptomyces rimosus was studied in batch and fed-batch cultures in shake flask and bioreactor levels using semi-defined medium. First, the effect of glucose concentration on OTC production and growth kinetics was studied intensively. The optimal glucose concentration in the medium was 15 g/L. Higher glucose concentrations supported higher biomass production by less volumetric and specific antibiotic production. Based on these data, cultivations were carried out at semi-industrial scale 15 L bioreactor in batch culture. At bioreactor level, cell growth and OTC production were higher compared to the shake flask culture by about 18 and 38%, respectively. During the bioreactor cultivation, glucose was totally consumed after only 48 h. Thus, the fed-batch experiment was designed for mono-glucose feeding and complete medium feeding to increase the OTC production by overcoming carbon limitations. The results showed that the fed-batch culture using constant glucose feeding strategy with rate of 0.33 g/L/h produced 1072 mg/L. On the other hand, feeding with complete medium resulted in 45% higher biomass but less OTC production by about 26% compared to mono-glucose fed culture. A further improvement in this process was achieved in by keeping the dissolved oxygen (DO) value at 60% saturation by cascading the glucose feeding pump with the DO controller. The later feeding strategy resulted in higher antibiotic production, reaching 1414 mg/L after 108 h.

Survivorship and feeding preferences among size classes of outplanted sea urchins, Tripneustes gratilla, and possible use as biocontrol for invasive alien algae.

We investigate the survivorship, growth and diet preferences of hatchery-raised juvenile urchins, Tripneustes gratilla, to evaluate the efficacy of their use as biocontrol agents in the efforts to reduce alien invasive algae. In flow-through tanks, we measured urchin growth rates, feeding rates and feeding preferences among diets of the most common invasive algae found in Kāneʻohe Bay, Hawaiʻi: Acanthophora spicifera, Gracilaria salicornia, Eucheuma denticulatum and Kappaphycus clade B. Post-transport survivorship of outplanted urchins was measured in paired open and closed cages in three different reef environments (lagoon, reef flat and reef slope) for a month. Survivorship in closed cages was highest on the reef flat (∼75%), and intermediate in the lagoon and reef slope (∼50%). In contrast, open cages showed similar survivorship on the reef flat and in the lagoon, but only 20% of juvenile urchins survived in open cages placed on the reef slope. Urchins grew significantly faster on diets of G. salicornia (1.58 mm/week ± 0.14 SE) and Kappaphycus clade B (1.69 ± 0.14 mm/wk) than on E. denticulatum (0.97 ± 0.14 mm/wk), with intermediate growth when fed on A. spicifera (1.23 ± 0.11 mm/wk). Interestingly, urchins display size-specific feeding preferences. In non-choice feeding trials, small urchins (17.5–22.5 mm test diameter) consumed G. salicornia fastest (6.08 g/day ± 0.19 SE), with A. spicifera (4.25 ± 0.02 g/day) and Kappaphycus clade B (3.83 ± 0.02 g/day) intermediate, and E. denticulatum was clearly the least consumed (2.32 ± 0.37 g/day). Medium-sized (29.8–43.8 mm) urchins likewise preferentially consumed G. salicornia (12.60 ± 0.08 g/day), with less clear differences among the other species in which E. denticulatum was still consumed least (9.35 ± 0.90 g/day). In contrast, large urchins (45.0–65.0 mm) showed no significant preferences among the different algae species at all (12.43–15.24 g/day). Overall consumption rates in non-choice trials were roughly equal to those in the choice trials, but differences among feeding rates on each species were not predictive of feeding preferences when urchins were presented all four species simultaneously. In the choice feeding trials, both small and medium urchins clearly preferred A. spicifera over all other algae (roughly twice as much consumed as any other species). Again, however, differences were less pronounced among adult urchins, with adults showing a significant preference for A. spicifera and Kappaphycus clade B compared to the other two algal species. These findings indicate that outplanted urchins are surviving on the reef flats and eating a variety of alien invasive algae as intended. Although juvenile urchins show stronger feeding preferences, these animals grow quickly, and adult urchins are more generalist herbivores that consume all four alien invasive algae.

Effects of human food grade titanium dioxide nanoparticle dietary exposure on Drosophila melanogaster survival, fecundity, pupation and expression of antioxidant genes

The fruitfly, Drosophila melanogaster was exposed to the human food grade of E171 titanium dioxide (TiO2). This is a special grade of TiO2 which is frequently omitted in nanotoxicology studies dealing with TiO2, yet it is the most relevant grade regarding oral exposure of humans. D. melanogaster larvae were exposed to 0.002 mg mL−1, 0.02 mg mL−1, 0.2 mg mL−1, and 2 mg mL−1 of TiO2 in feeding medium, and the survival, fecundity, pupation time, and expression of genes involved in oxidative stress response were monitored. TiO2 did not affect survival but significantly increased time to pupation (p < 0.001). Fecundity of D. melanogaster was unaffected by the treatment. Expression of the gene for catalase was markedly downregulated by the treatment, while the effect on the downregulation of superoxide dismutase 2 was less pronounced. After four days of dietary exposure TiO2 was present in a significant amount in larvae, but was not transferred to adults during metamorphosis. Two individuals with aberrant phenotype similar to previously described gold nanoparticles induced mutant phenotypes were detected in the group exposed to TiO2. In general, TiO2 showed little toxicity toward D. melanogaster at concentrations relevant to oral exposure of humans.

The use of date waste for lactic acid production by a fed-batch culture using Lactobacillus casei subsp. rhamnosus.

The production of lactic acid from date juice by Lactobacillus caseisubsp. rhamnosus in batch and fed-batch cultures has been investigated. The fed-batch culture system gave better results for lactic acid production and volumetric productivity. The aim of this work is to determine the effects of the feeding rate and the concentration of the feeding medium containing date juice glucose on the cell growth, the consumption of glucose and the lactic acid production by Lactobacillus casei subsp. rhamnosus in fed-batch cultures. For this study, two concentrations of the feeding medium (62 and 100 g/L of date juice glucose) were tested at different feeding rates (18, 22, 33, 75 and 150 mL/h). The highest volumetric productivity (1.3 g/L.h) and lactic acid yield (1.7 g/g) were obtained at a feeding rate of 33 mL/h and a date juice glucose concentration of 62 g/L in the feeding medium. As a result, most of the date juice glucose was completely utilised (residual glucose 1 g/L), and a maximum lactic acid production level (89.2 g/L) was obtained.

The pigment characteristics and productivity shifting in high cell density culture of Monascus anka mycelia.

BackgroundMonascus mycelia and pigments are promising sources of food and medicine with their potential pharmaceutical values and health-improving functions. Using high cell density fermentation of Monascus spp. to achieve higher mycelium and yellow pigment production is worthy to be researched. In this study, the characteristics and productivity shifting of pigments in high cell density culture of Monascus anka GIM 3.592 were investigated.ResultsThe high yield of Monascus mycelia up to 39.77 g/L dry cell weight (DCW), which was achieved by fed-batch fermentation with the feeding medium containing C, N, P and trace elements, was four times higher than that of conventional batch culture. But the total pigment production decreased by 14.6 %, which suggested non-coupled growth. Potential novel yellow pigments accumulated constantly at the late stage of the fed-batch culture, which resulted in a shift in pigment characteristics so that yellow pigments became the dominant pigments. Citrinin production was extremely low and independent of feeding ingredients.ConclusionsThis study provided a suitable fermentation strategy to produce functional Monascus mycelia with a high proportion of yellow pigments in high cell density culture. For the first time, it reported the pigment productivity and characteristics shifting in high cell density culture of Monascus.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-015-0183-3) contains supplementary material, which is available to authorized users.

Continuous gas fermentation by Acetobacterium woodii in a submerged membrane reactor with full cell retention

Acetogenic bacteria like Acetobacterium woodii represent an ancient group of anaerobic microorganisms which use hydrogen and carbon dioxide to produce acetate. Cell concentrations and space–time yields are usually low in gas fermentations. A standard stirred‑tank bioreactor with continuous gas supply was equipped with a customized submerged microfiltration unit. A. woodii showed similar growth behavior with an initial maximal growth rate of 1.2d−1 in continuous gas fermentations with full cell retention and varying dilution rates. A steady increase of cell mass concentrations was observed with the highest biomass formation at the highest dilution rate. By contrast the final acetate concentrations were lowest at the highest dilution rate. The highest final acetate space–time yield of 148gl−1d−1 was measured at the highest dilution rate (increase by factor 8 compared to a standard batch process or by factor 37 compared to published data). The highest reported cell concentration of A. woodii in gas fermentations of nearly 14gl−1 cell dry weight was achieved in the submerged membrane bioreactor with increased yeast extract concentrations in the feed medium. Product inhibition was observed when acetate concentrations exceeded 8–12gl−1 causing a steady decrease in cell mass specific acetate production rates.