Foam and Its Mitigation in Fermentation Systems

Background: The proportion of biogas in the mix of renewable energies is still remarkably high. The process of anaerobic digestion (AD) provides the basis of biogas production but often leads to excessive foaming. Identifying the reasons for foaming is difficult for biogas plant operators because many factors may play a role. It is therefore difficult for laboratory research to give answers to this specific problem, as the consistency of the digestate itself plays a crucial part in the foam formation process. Hence, careful investigation of foaming in full-scale biogas plants is important in order to identify the main causes and to develop strategies for the prevention of foaming.

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“…It is known that yeast supports foam formation [39]. For this reason, yeast is normally loaded in small amounts into the digester.…”

Section: Biogas Plant Bp Bmentioning

confidence: 99%

Foam formation in full-scale biogas plants processing biogenic waste

Moeller

Görsch

2015

Energ Sustain Soc

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“…As much as 30 mL/L of P2000 was required to control foaming above the 3 mL/L initially batched. Foaming, and associated foam control, was a scale-up hindrance, contamination risk, and downstream isolation challenge [20][21][22][23][24][25].…”

Section: Resultsmentioning

confidence: 99%

Pilot-scale process development and scale up for antifungal production

Junker

Walker

Hesse

et al. 2008

Bioprocess Biosyst Eng

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A pilot-scale fermentation was developed for an antifungal compound produced by a filamentous fungus. Replacement of galactose with lactose (20-fold cost savings) and a threefold phosphate reduction (15 to 5 g/L) improved productivity 2.5-fold. Addition of supplements--glycine, cobalt chloride, and trace elements--resulted in a further twofold productivity increase, greater process robustness, and less foaming which reduced antifoam addition tenfold (30 to <3 mL/L). Mid-cycle lactose limitations were addressed by raising initial lactose levels (40 to 120 g/L) resulting in another twofold productivity increase. Overall, peak titers increased tenfold from 45 +/- 9 to 448 +/- 39 mg/L, and productivities improved from 3 to 25 mg/L day. Despite its high productivity, process scale up was challenged by high broth viscosity (5,000-6,000 cP at 16.8 s(-1)). Gassed power requirements at the 600 L scale (4.7 kW/1,000 L) exceeded available power at the 15,000 L scale (3.0 kW/1,000 L), and broth transfer to the downstream isolation facility was hindered. Mid-cycle broth dilution with up to five 10 vol% additions of 12 wt% lactose solution or whole medium-reduced viscosity three- to fivefold (1,000-1,500 cP at 16.8 s(-1)), gassed power within scale-up limits (2.5 kW/1,000 L), and peak titer by up to 45%. The process was scaled up to the 15,000 L working volume based on constant aeration rate (vvm) and peak impeller tip speed, raising superficial velocities at similar shear. This strategy maximized mass transfer rates at target gassed power per unit volume levels, and along with controlled broth viscosity, precluded multiple dilution additions. A final titer of 333 mg/L with one dilution addition was achieved, somewhat lower than expected, likely owing to inhibition from some unmeasured volatile compound (not believed to be carbon dioxide) during an extended period of high back-pressure in the early production phase.

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“…Consistent with these observations, in our work, the CMC was reached after approximately 18 h, and foam formation appeared a little after (24 h). Foam formation is important in fermentation processes devoted to the production of extracellular biosurfactants; in fact, acting as a reservoir, foam makes biosurfactant recovery easier (Junker, 2007).…”

Section: A B C Production Of Biosurfactant In the Bench-scale Bioreactormentioning

confidence: 99%

Influence of toluene and salinity on biosurfactant production by Bacillus sp.: scale up from flasks to a bench-scale bioreactor

Souza

Vessoni-Penna

Arni³

et al. 2017

Braz. J. Chem. Eng.

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-To select the best biosurfactant producer, Pseudomonas putida, Bacillus megatherium, Bacillus licheniformis and Bacillus subtilis were cultured in flasks on media with different salinity [low salinity (LS), Bushnell-Haas (BH) and artificial sea water (SW) media] supplemented or not with toluene as a model pollutant. Toluene inhibited the growth of all microorganisms and stimulated the biosurfactant production. B. subtilis exhibited the best performance, being able to lower the surface tension (ST) in the LS medium to 65.5 mN/min in the absence of toluene, and to 46.5 mN/min in the BH medium in the presence of toluene, corresponding to ST reductions of 13.0 and 27.5 mN/m, respectively. Scaling up the process to a bench-scale fermentor, the best results were obtained in the LS medium, where B. subtilis was able to reduce the toluene concentration from 26.0 to 4.3 g/L within 12 h and ST by 17.2 mN/m within 18 h. The results of this study point out that B. subtilis is an interesting biosurfactant producer, which could be used in the bioremediation of toluene-contaminated water.

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Foam and Its Mitigation in Fermentation Systems

Cited by 86 publications

References 76 publications

Foam formation in full-scale biogas plants processing biogenic waste

Foam formation in full-scale biogas plants processing biogenic waste

Pilot-scale process development and scale up for antifungal production

Influence of toluene and salinity on biosurfactant production by Bacillus sp.: scale up from flasks to a bench-scale bioreactor

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