Effect of acetic acid on lipid accumulation by glucose‐fed activated sludge cultures

Mondala, Andro; Hernández, Rafael; French, Todd; McFarland, Linda; Sparks, Darrell; Holmes, William E.; Haque, M. Zahurul

doi:10.1002/jctb.2760

Cited by 7 publications

(6 citation statements)

References 35 publications

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“…Acetic acid thus served as both pH moderator and carbon feedstock. Considering that protonated acetic acid crosses the cellular membrane through passive transport and affects intracellular pH balance (20,21), the fermentation pH was maintained at 7, which is higher than the pK a of acetic acid. In this way, acetic acid existed primarily in the salt form, which is less toxic to the cells.…”

Section: Resultsmentioning

confidence: 99%

Application of metabolic controls for the maximization of lipid production in semicontinuous fermentation

Liu

Qiao

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Acetic acid can be generated through syngas fermentation, lignocellulosic biomass degradation, and organic waste anaerobic digestion. Microbial conversion of acetate into triacylglycerols for biofuel production has many advantages, including low-cost or even negative-cost feedstock and environmental benefits. The main issue stems from the dilute nature of acetate produced in such systems, which is costly to be processed on an industrial scale. To tackle this problem, we established an efficient bioprocess for converting dilute acetate into lipids, using the oleaginous yeast Yarrowia lipolytica in a semicontinuous system. The implemented design used low-strength acetic acid in both salt and acid forms as carbon substrate and a cross-filtration module for cell recycling. Feed controls for acetic acid and nitrogen based on metabolic models and online measurement of the respiratory quotient were used. The optimized process was able to sustain high-density cell culture using acetic acid of only 3% and achieved a lipid titer, yield, and productivity of 115 g/L, 0.16 g/g, and 0.8 g·L −1 ·h −1 , respectively. No carbon substrate was detected in the effluent stream, indicating complete utilization of acetate. These results represent a more than twofold increase in lipid production metrics compared with the current best-performing results using concentrated acetic acid as carbon feed.lipid production | acetate | tangential filtration | dynamic modeling | exhaust gas analysis

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Section: Resultsmentioning

confidence: 99%

Application of metabolic controls for the maximization of lipid production in semicontinuous fermentation

Liu

Qiao

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…29 With the inoculation rate increase, the initial acetic acid concentration decreased, which resulted in a lower inhibition effect on the biomass growth in the logarithmic phase. 40 Similarly, other toxic secondary metabolites as well as the solvent product from the ABE fermentation could also lead to a more severe inhibition to cell growth when the inoculation rate decreased. In the stable stage, the lack of nutrients led to the decrease of the biomass productivity in the high inoculation rate cases.…”

Section: Two-stage Abe Fermentationmentioning

confidence: 99%

“…Fortunately, the organic acid by-products in the fermentation broth could be metabolized as a carbon source by several oleaginous strains. [37][38][39][40][41] Aiming to reuse the high organics content wastewater from ABE fermentation processes and convert them into valuable advanced bio-fuels, while further decreasing the COD level, in the present study, an effective and energy saving biochemical process was performed to emphasize the 'green benefits' (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Co-generation of bio-butanol and bio-lipids under a hybrid process

et al. 2016

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“…Previous studies indicated that activated sludge microbial consortia (ASMC) are capable of accumulating lipids when cultivated in a N-limited environment with abundant carbon sources, particularly when C/N mass ratio is ≥40. − These previous works had the ultimate goal of utilizing existing WWTPs for production of microbial lipids, which can be used as bioenergy and/or biomaterial precursors. , This goal entails addition of aerobic lipid-accumulation unit(s) that utilizes additional carbon source or substrate to enhance microbial lipids production in ASMC. However, utilization of expensive substrates (e.g., sugars, lignocellulosic biomass hydrolyzates) could account for up to 75% of the costs of microbial lipids and thus, presents a major drawback in its large scale implementation …”

Section: Introductionmentioning

confidence: 99%

Microbial Lipid Production through Integrated Anaerobic-Aerobic Biotreatment Process: An Urban-Based Biorefinery Concept

Revellame

Zappi

Hernández

et al. 2021

ACS Sustainable Chem. Eng.

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Current operations within wastewater treatment plants (WWTPs), particularly the anaerobic digestion and activated sludge processes, can be tapped for production of microbial lipids. This can be accomplished by directing the anaerobic digestion to produce short chain carboxylic acids (SCCAs) that can then be used as substrates for lipid production using activated sludge microbial consortium in an add-on aerobic lipid production unit (similar to an activated sludge process). This study was conducted to assess the suitability of a Test Medium (previously proven suitable for aerobic lipid production in activated sludge) for the proposed integrated system. Results showed that, when used for anaerobic fermentation, the Test medium produced 0.48 g-SCCAs/g-substrate that includes acetic, butyric, and predominantly (∼89 wt%), lactic acid. Subsequently, the Test Medium resulted to a peak lipid yield of ∼0.17 g/g-SCCAs. Complete substrate consumptions were observed without pH control when the Test Medium was used for both bioprocesses. These results suggest the suitability of the Test Medium for the integrated system for microbial lipids production. This could significantly simplify the implementation of the proposed integrated system, which could provide the basis for future urban biorefineries through existing WWTPs.

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Effect of acetic acid on lipid accumulation by glucose‐fed activated sludge cultures

Cited by 7 publications

References 35 publications

Application of metabolic controls for the maximization of lipid production in semicontinuous fermentation

Application of metabolic controls for the maximization of lipid production in semicontinuous fermentation

Co-generation of bio-butanol and bio-lipids under a hybrid process

Microbial Lipid Production through Integrated Anaerobic-Aerobic Biotreatment Process: An Urban-Based Biorefinery Concept

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