Exploring the limits of carbohydrate conversion and product formation in open mixed culture fermentation. Issue 3 (June 2022)

• Record Type: Journal Article
• Authors: Rafay, Ramis; Allegue, Tomás; Fowler, S Jane; Rodríguez, Jorge
• Is Part Of: Journal of environmental chemical engineering. Volume 10:Issue 3(2022)
• Publication Date: 2022-06
• Subjects: ASV amplicon sequence variant -- COD chemical oxygen demand -- CSTR continuously stirred tank reactor -- HPLC high-performance liquid chromatography -- HRT hydraulic retention time -- MCF mixed culture fermentation -- PCoA principal coordinate analysis -- RI refractive index -- SCCA short-chain carboxylic acid -- SRT sludge retention time -- TSS total suspended solid -- VSS volatile suspended solids; Short-chain carboxylic acids -- Substrate concentration -- Undissociated acids -- Granular biomass -- Valerate production; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2022.107513
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: The industrial large-scale application of open mixed culture carbohydrate fermentation processes requires a better understanding of their capacity limits and product spectra. This work aims to explore these limits through the operation of two lab-scale fermenters at increasing influent glucose concentrations in continuous mode and using constant operating conditions (HRT = 20 h; pH 5.4; 30 °C). In one fermenter, glucose concentration increases were slow, in order to determine representative product yields. In the other fermenter, increases were faster, aiming also at gaining other operational insights along with a consistency validation of product yields. Different glucose concentrations led to consistent product yields in both fermenters. Full glucose conversion limit was reached at 33 gCOD Lfeed -1, with 32 mM of undissociated acids present. After glucose fermentation saturation, up to 10.6 gCOD L -1 lactate accumulation was observed. In both reactors, a glucose concentrations of 33 gCOD Lfeed -1 led to the formation of granular biomass, with which full glucose conversion resumed up to 38 gCOD Lfeed -1 . In terms of products, at low glucose concentrations with only suspended biomass, the main products were acetate and butyrate, while at higher concentrations with granular biomass, the main products shifted to propionate and valerate. The similar microbial communities and products between both reactors suggest that a shorter startup time to full capacity loading is possible, which is relevant for large scale industrial implementation. Graphical Abstract: ga1 Highlights: Consistent product yield and microbial communities observed in both fermenters. Glucose fermentation saturation onset occurred at 32 mM of undissociated acids. Up to 13.8 g COD L -1 lactate accumulation during glucose fermentation saturation. Glucose fermentation capacity increased simultaneously to granules accumulation. 8.3 g COD L -1 of valerate were produced at 38 g COD Lfeed -1 .