High‐rate volatile fatty acid (VFA) production by a granular sludge process at low pH

Abstract

Volatile fatty acids (VFA) are proposed platform molecules for the production of basic chemicals and polymers from organic waste streams. In this study we developed a granular sludge process to produce VFA at high rate, yield and purity while minimizing potential operational costs. A lab-scale anaerobic sequencing batch reactor (ASBR) was fed with 10 g l(-1) glucose as model substrate. Inclusion of a short (2 min) settling phase before effluent discharge enabled effective granulation and very high volumetric conversion rates of 150-300 gCOD l(-1) d(-1) were observed during glucose conversion. The product spectrum remained similar at the tested pH range with acetate and butyrate as the main products, and a total VFA yield of 60-70% on chemical oxygen demand (COD) basis. The requirement for base addition for pH regulation could be reduced from 1.1 to 0.6 mol OH(-) (mol glucose)(-1) by lowering the pH from 5.5 to 4.5. Solids concentrations in the effluent were 0.6 ± 0.3 g l(-1) but could be reduced to 0.02 ± 0.01 g l(-1) by introduction of an additional settling period of 5 min. The efficient production of VFA at low pH with a virtually solid-free effluent increases the economic feasibility of waste-based chemicals and polymer production. Biotechnol.

Electrochemically Driven Fermentation of Organic Substrates with Undefined Mixed Microbial Cultures

“…The spectrum of attained fermentation products is consistent with that reported in ar ecent study, [28] whereby the fermentation of glucose by am ixed microbial culture (MMC) was studied at pH ranging from 4.5 to 5.5. The spectrum of attained fermentation products is consistent with that reported in ar ecent study, [28] whereby the fermentation of glucose by am ixed microbial culture (MMC) was studied at pH ranging from 4.5 to 5.5.…”

Semicontinuous anaerobic digestion of protease pretreated Chlorella biomass for volatile fatty acids production

“…Volatile fatty acids (VFAs) are valuable building blocks for the chemical industry due to their wide applications in fields including food preservation, cosmetics, textiles and pharmaceuticals. VFAs have attracted the attention of the scientific community in the so‐called carboxylate platform . These compounds have been traditionally obtained by petrochemical means.…”

“…Another possible approach to inhibit the methanogenesis step might be to take into account the metabolic features of the different species involved in the AD process. In this sense, the slow growth and sensitivity of methanogenic archaea with regard to those of anaerobic bacteria can be used as a tool to mediate methanogenesis inhibition . Operational conditions such as temperature (T), organic loading rate (OLR) and hydraulic retention time (HRT) can be manipulated to affect population dynamics within the bioreactor to favor the activity and prevalence of those species in charge of VFA production …”

“…VFAs have attracted the attention of the scientific community in the so-called carboxylate platform. [1][2][3] These compounds have been traditionally obtained by petrochemical means. Nevertheless, the increasing search for renewable sources together with environmental concerns is boosting the need of developing new production models.…”

“…In this sense, the slow growth and sensitivity of methanogenic archaea with regard to those of anaerobic bacteria can be used as a tool to mediate methanogenesis inhibition. 3 Operational conditions such as temperature (T), organic loading rate (OLR) and hydraulic retention time (HRT) can be manipulated to affect population dynamics within the bioreactor to favor the activity and prevalence of those species in charge of VFA production. 9 Biogas production has traditionally used AD, and thus, the carboxylate platform requires revisiting the AD process.…”