Development of a low-cost cellulase production process using Trichoderma reesei for Brazilian biorefineries

Abstract

BackgroundDuring the past few years, the first industrial-scale cellulosic ethanol plants have been inaugurated. Although the performance of the commercial cellulase enzymes used in this process has greatly improved over the past decade, cellulases still represent a very significant operational cost. Depending on the region, transport of cellulases from a central production facility to a biorefinery may significantly add to enzyme cost. The aim of the present study was to develop a simple, cost-efficient cellulase production process that could be employed locally at a Brazilian sugarcane biorefinery.ResultsOur work focused on two main topics: growth medium formulation and strain improvement. We evaluated several Brazilian low-cost industrial residues for their potential in cellulase production. Among the solid residues evaluated, soybean hulls were found to display clearly the most desirable characteristics. We engineered a Trichoderma reesei strain to secrete cellulase in the presence of repressing sugars, enabling the use of sugarcane molasses as an additional carbon source. In addition, we added a heterologous β-glucosidase to improve the performance of the produced enzymes in hydrolysis. Finally, the addition of an invertase gene from Aspegillus niger into our strain allowed it to consume sucrose from sugarcane molasses directly. Preliminary cost analysis showed that the overall process can provide for very low-cost enzyme with good hydrolysis performance on industrially pre-treated sugarcane straw.ConclusionsIn this study, we showed that with relatively few genetic modifications and the right growth medium it is possible to produce considerable amounts of well-performing cellulase at very low cost in Brazil using T. reesei. With further enhancements and optimization, such a system could provide a viable alternative to delivered commercial cellulases.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-017-0717-0) contains supplementary material, which is available to authorized users.

Reexamining opportunities for therapeutic protein production in eukaryotic microorganisms

“…To address these considerations, a new approach to recombinant protein production for therapeutic biologic products may be needed. Looking to other industries for inspiration, the production of industrial enzymes has many similarities to the production of therapeutic proteins, but is dominated by processes that generate metric tons of material per batch at significantly lower cost (Singhania, Patel, & Pandey, ), as low as $2–10 per kilogram (Ellilä et al, ). These processes are built around microbial host organisms which grow quickly and robustly in fermenters up to 300,000 L in volume, with titers as high as 100 g/L for some enzymes (Cherry & Fidantsef, ).…”

Mutation of a Conserved Alanine Residue in Transcription Factor AraR Leads to Hyperproduction of α‐l‐Arabinofuranosidases in Penicillium oxalicum

“…Considering that the mutated alanine is highly conserved in AraR homologs, the strategy was expected to be applied for the engineering of other α‐ l ‐arabinofuranosidase‐producing fungi possessing AraR. In addition, the valine residue three amino acids upstream of the mutated alanine, which could also render XlnR/XYR1 constitutively active when mutated to phenylalanine, was substituted by a leucine residue in AraR (Figure S1, Supporting Information). An L–F mutation at this site might also turn AraR constitutively active.…”

Production of Cellulases by Solid State Fermentation of Different Agricultural Residues Using Humicola insolens MTCC 1433

“…These fungi were able to degrade agricultural wastes at faster rate by degrading cellulose. Ellila et al, (2017) developed a simple, cost efficient cellulase production process that could be employed locally at a Brazilian sugarcane biorefinery. The low cost industrial residues were used to evaluate their potential for cellulase production and among the solid residues tested, soybean hulls showed the most desirable characteristics.…”

“…The operational cost of enzymes results from two main factors, i.e. quality of enzyme required to hydrolyze biomass and cost of each kilogram of enzyme to the end user (Ellila et al, 2017). Utilization of agricultural residues as substrates can help to reduce production cost of microbial enzymes and in addition, help in the management of various agricultural residues which are generated in abundance and difficult to dispose-off (Bajaj et al, 2014).…”