Bioreactor design for enzymatic hydrolysis of biomass under the biorefinery concept

Abstract

The dependence on non-renewable resources, particularly fossil fuels, has awaken a growing interest in research of sustainable alternative energy sources, such as bioethanol. The production of bioethanol from lignocellulosic materials comprises three main stages, starting with a pretreatment, followed by an enzymatic hydrolysis step where fermentable sugars are obtained for the final fermentation process. Enzymatic hydrolysis represents an essential step in the bioethanol production, however there are some limitations in it that hinders the process to be economically feasible. Different strategies have been studied to overcome these limitations, including the enzyme recycling and the utilization of high solids concentrations. Several investigations have been carried out in different bioreactor configurations with the aim to obtain higher yields of glucose in the enzymatic hydrolysis stage; however, the commonest are Stirred Tank Bioreactors (STBR) and Membrane Bioreactors (MBR). In general, the key criteria for a bioreactor design include adequate mass transfer, low shear stress, and efficient mixing that allows the appropriated interaction between the substrate and the enzyme. Therefore, this review will address the main aspects to be considered for a bioreactor design, as well as, the operational conditions, some characteristics and mode of operating strategies of the two main bioreactors used in the enzymatic hydrolysis stage. Moreover, two types of pneumatically agitated bioreactors, namely bubble column and gas-lift bioreactors, are discussed as promising alternatives to develop enzymatic saccharification due to their low energy consumption compared with STBR.

Enhancement and modeling of enzymatic hydrolysis on cellulose from agave bagasse hydrothermally pretreated in a horizontal bioreactor

“…However, during the EH, the presence of a wide range of compounds restrict the action of cellulase enzymes, including hemicellulose, phenolic compounds, acetyl groups and lignin, which act as physical barriers for the cellulases action. Also, lignin presence may cause cellulases deactivation, due to non-productive adsorption of the enzymes into lignin's surface (Pino et al, 2018). Moreover, it has been demonstrated that cellulases experience feedback inhibition by glucose and cellobiose (Andrić, Meyer, Jensen, & Dam-Johansen, 2010).…”

“…1016/j.carbpol.2019.01.111 Received 14 December 2018 Received in revised form 29 January 2019; Accepted 31 January 2019 loadings (cellulose), a highly viscous slurry is formed, which reduces the mixing efficiency and affect the substrate (cellulose)-enzyme (cellulase) interaction (Andrić et al, 2010;Du et al, 2014). Therefore, different bioreactor design strategies have been development to overcome mass transfer limitations at high solid loadings (Pino et al, 2018). Horizontal bioreactors have been stated as a promising alternative to enhance high solid loading enzymatic hydrolysis (Dasari, Dunaway, & Berson, 2009;Du et al, 2014).…”

Production of Biomass-Degrading Enzymes by Trichoderma reesei Using Liquid Hot Water-Pretreated Corncob in Different Conditions of Oxygen Transfer

“…This is mainly due to the high production cost of the enzymes, the low yields, and the considerable quantities of enzymes that are required during the process. For example, in the bioethanol production, the enzyme cost represents about 15-28% of the bioethanol selling price, or 20% of the overall bioethanol production costs [1]. Additionally, it has been reported that the biggest cost in the cellulase production is in the raw materials and consumables and that this cost varies according to the production approach, being the integrated method, where the cellulose is used as raw material to produce the cellulase, the most cost-effective compared to others that use glucose as raw material [2].…”

Review of Solvents Based on Biomass for Mitigation of Wax Paraffin in Indonesian Oilfield

“…Hydrolysis consists of the degradation of polysaccharides in aqueous media that can be catalyzed by enzymes, acids, or bases to produce glucose [13,36,42,[49][50][51][52][53][54][55][56][57][58][59][60][61][62][63]. The hydrolysis result will depend on the reaction of enzymes and compounds [64][65][66][67].…”