Biofilm reactors for industrial bioconversion processes: employing potential of enhanced reaction rates

Abstract

This article describes the use of biofilm reactors for the production of various chemicals by fermentation and wastewater treatment. Biofilm formation is a natural process where microbial cells attach to the support (adsorbent) or form flocs/aggregates (also called granules) without use of chemicals and form thick layers of cells known as "biofilms." As a result of biofilm formation, cell densities in the reactor increase and cell concentrations as high as 74 gL -1 can be achieved. The reactor configurations can be as simple as a batch reactor, continuous stirred tank reactor (CSTR), packed bed reactor (PBR), fluidized bed reactor (FBR), airlift reactor (ALR), upflow anaerobic sludge blanket (UASB) reactor, or any other suitable configuration. In UASB granular biofilm particles are used. This article demonstrates that reactor productivities in these reactors have been superior to any other reactor types. This article describes production of ethanol, butanol, lactic acid, acetic acid/vinegar, succinic acid, and fumaric acid in addition to wastewater treatment in the biofilm reactors. As the title suggests, biofilm reactors have high potential to be employed in biotechnology/bioconversion industry for viable economic reasons. In this article, various reactor types have been compared for the above bioconversion processes.

Continuous succinic acid production from xylose by Actinobacillus succinogenes

“…Filled circle glucose study, filled triangle xylose study, In (D) and (F): open circle glucose study, open triangle xylose study studies were conducted in batch or repeat-batch mode and the high productivities achieved in this study highlight the benefits of operating continuously. Also, the use of biofilm to increase cell densities and enhance productivities [39] is clearly demonstrated in the current study.…”

“…In biofilm fermentations, cell mass accumulates in the fermenter [39], and erosion and sloughing of biofilm [33] cause segments to exit the fermenter unpredictably. As such, DCW measurements either do not account for biomass incorporated into the biofilm or contain biofilm fragments of accumulated biomass that overestimate mass in continuous fermentations [40], and cell growth terminates at a CSA of around 13 g L -1 in batch fermentations [41].…”

Succinic acid-producing biofilms of Actinobacillus succinogenes: reproducibility, stability and productivity

“…Currently, the main industrial application for biofilm reactors is for the treatment of wastewater and off-gas (Qureshi et al 2005). A number of review papers recently highlighted the potential of single culture biofilm reactors for the production of speciality and bulk chemicals (Cheng et al 2010;Gross et al 2007;Qureshi et al 2005;Rosche et al 2009).…”

“…A number of review papers recently highlighted the potential of single culture biofilm reactors for the production of speciality and bulk chemicals (Cheng et al 2010;Gross et al 2007;Qureshi et al 2005;Rosche et al 2009). The self-immobilisation nature of some microbial strains has the advantage that cell-retainment within a bioreactor can be achieved without any active cell-separation scheme.…”

Application of Insoluble Fibroin Film as Conditioning Film for Biofilm Formation

“…On the other hand, biofilms are particularly suitable for use in bioremediation and biofilm reactors. (29,30) Some advantages of the application of biofilms in a reactor are that comparatively high productivities and high cell densities are achieved. (30) In these reactors, reaction rates are usually high as compared with those in the other types of reactor.…”