Continuous enzymatic hydrolysis of lignocellulosic biomass in a membrane‐reactor system

Abstract

BACKGROUND:Converting abundant lignocellulosic biomass to sugars as fungible precursors to fuels and chemicals has the potential to diversify the supply chain for those products, but further process improvements are needed to achieve economic viability. In the current work, process intensification of the key enzymatic hydrolysis unit operation is demonstrated by means of a membrane reactor system that was operated continuously.RESULTS: Lignocellulosic biomass (pretreated corn stover) and buffered enzyme solution were fed to a continuously stirred-tank reactor, and clarified sugar solution was withdrawn via a commercial tubular ultrafiltration membrane. The membrane permeance decline and membrane cleaning efficacy were studied and did not vary significantly when increasing fraction insoluble solids (FIS) from 2.5% to 5%. Continuous enzymatic hydrolysis was

Enzymatic Hydrolysis of Sugarcane Bagasse in Aqueous Two-Phase Systems (ATPS): Exploration and Conceptual Process Design

“…Although the conventional hydrolysis does not indicate a desorption of enzymes after the reaction, PEG has been demonstrated to favor enzyme adsorption on the surface of the biomass, preventing the binding to the lignin (Malmsten and Van Alstine, 1996 ; Haven and Jørgensen, 2013 ). This feature of the ATPS could promote the recycle of enzymes and validate the hydrolysis model proposed by Stickel et al ( 2018 ), in which the concentration of free enzymes increases with the decrease of substrate (glucan). Moreover, the non-selective partition and adsorption of the different enzymatic activities tested suggest a constant recycled cocktail composition.…”

“…Consequently, the recovery efficiency should be assessed in terms of maintenance of enzymatic activity after ultrafiltration (retentate stream), and considering the number of ultrafiltration cycles needed to repartition glucose and obtain the desirable recovery of this product. When assessing the enzymatic activity of the retentate to be recycled to the system, it is also important to regard the theoretical loss of enzymes in the permeate and purge streams (Stickel et al, 2018 ).…”

Process Design and Economics for the Conversion of Lignocellulosic Biomass to Hydrocarbon Fuels and Coproducts: 2018 Biochemical Design Case Update; Biochemical Deconstruction and Conversion of Biomass to Fuels and Products via Integrated Biorefinery Pathways

“…Alternatively, recent NREL research has begun investigating the more novel continuous enzymatic hydrolysis approach wherein hydrolysis is initiated in a continuous stirred tank reactor (CSTR) vessel connected through a pump-around loop to a microfilter, which continuously removes sugars as they're produced while retaining the unhydrolyzed solids. This improves hydrolysis kinetics by reducing sugar feedback inhibition, allowing for lower hydrolysis volumes, higher sugar yields, and/or lower enzyme loadings based on NREL proof-of-concept experimental work at bench scale (3 L reactor volumes operated over 80 hours) [47]. The residual solids from one CSTR step are routed to a subsequent CSTR with the same setup, and this process is repeated several times (in this design, using three CEH reactors in series).…”

A two-phase substrate model for enzymatic hydrolysis of lignocellulose: application to batch and continuous reactors

“…As one of several process steps in the biochemical conversion of biomass to fuels and chemicals, enzymatic hydrolysis (EH) continues to contribute significantly to the total conversion cost. Traditionally, the unit operation (process step) of EH has been performed and analyzed as a batch operation [6], but, more recently, there has been interest in alternative conversion strategies in order to reduce enzyme usage and capital costs through process intensification [8, 22, 31, 34]. However, systematic development and economical evaluation of these novel processes are stymied by a lack of accessible reaction-kinetics models.…”

“…This advanced reactor concept has potential, compared to batch reactors, to improve rates through reduced product inhibition while retaining enzyme within the reactor system, and to provide a solids-free sugar source for downstream upgrading. This system will be described in “Materials and methods” section and has been studied previously [31], although with a less-rigorous modeling approach. Batch experiments are used as the basis for parameter determination, the model is applied to the CSTR system using the mass-flow rates calculated by the control system, and sugar concentrations and insoluble solids fraction from continuous EH experiments are compared to model predictions.…”