Challenges and advances in the heterologous expression of cellulolytic enzymes: a review

Abstract

Second generation biofuel development is increasingly reliant on the recombinant expression of cellulases. Designing or identifying successful expression systems is thus of preeminent importance to industrial progress in the field. Recombinant production of cellulases has been performed using a wide range of expression systems in bacteria, yeasts and plants. In a number of these systems, particularly when using bacteria and plants, significant challenges have been experienced in expressing full-length proteins or proteins at high yield. Further difficulties have been encountered in designing recombinant systems for surface-display of cellulases and for use in consolidated bioprocessing in bacteria and yeast. For establishing cellulase expression in plants, various strategies are utilized to overcome problems, such as the auto-hydrolysis of developing plant cell walls. In this review, we investigate the major challenges, as well as the major advances made to date in the recombinant expression of cellulases across the commonly used bacterial, plant and yeast systems. We review some of the critical aspects to be considered for industrial-scale cellulase production.

Progress and obstacles in the production and application of recombinant lignin-degrading peroxidases

“…16,17 In contrast, the mechanisms and interactions of lignin-degrading enzymes (especially peroxidases) are poorly characterized. Even so, many recombinant lignin-degrading enzymes from diverse fungal ( Table 1) and bacterial (Table 2) sources have been expressed in different host organisms, although it is challenging to achieve high yields and satisfactory catalytic activity due to the complex secondary and tertiary structures of such enzymes.…”

Improved ethanol production from biomass by a rumen metagenomic DNA fragment expressed in Escherichia coli MS04 during fermentation

“…The sustainable and competitive production of lignocellulosic ethanol depends on several factors, including the improvement of expression levels and performance of recombinant cellulolytic enzymes that are responsible for releasing the fermentable sugars from cellulose during the saccharification step (Lambertz et al 2014). A major bottleneck for the competitive production of lignocellulosic ethanol is the high enzyme load during the saccharification step of pretreated lignocellulosic biomass (Gao et al 2011;Lambertz et al 2014).…”

Bioprospecting thermostable cellulosomes for efficient biofuel production from lignocellulosic biomass

“…The efficient enzymatic hydrolysis is dependent on the set of enzymes on the cellulosome, with the most effective enzyme composition being dependent on the respective substrate (Blouzard et al 2010;Chundawat et al 2011). Another obstacle is difficult and costly cultivation of native cellulosome-producing bacteria due to requirement of anaerobic conditions (Lambertz et al 2014).…”

“…Another challenge for cellulase production is the development of bioprocess with cost-effective titer of cellulase using cheap media (Shahriarinour et al 2011). Moreover, the problems with many cellulase-producing microorganisms are requirement of special culturing conditions and low product yield with secretion of some unwanted products (Lambertz et al 2014). Further, saccharification with the conventional mesophilic microorganisms remains challenging due to high enzyme loading to meet the industrial needs, long incubation period and lesser mass transfer at lower temperatures (Stern et al 2014;Rollin et al 2011).…”