Abstract
The mimicking of evolution on a laboratory timescale to enhance biocatalyst specificity, substrate utilization activity, and/or product formation, is an effective and well-established approach that does not involve genetic engineering or regulatory details of the microorganism. The present work employed an evolutionary adaptive approach to improve the lignocellulose deconstruction capabilities of the strain by inducing the expression of laccase, a multicopper oxidase, in Geobacillus sp. strain WSUCF1. This bacterium is highly efficient in depolymerizing unprocessed lignocellulose, needing no preprocessing/pretreatment of the biomasses. However, it natively produces low levels of laccase. After 15 rounds of serially adapting this thermophilic strain in the presence of unprocessed corn stover as the selective pressure, we recorded a 20-fold increase in catalytic laccase activity, at 9.23 ± 0.6 U/mL, in an adapted yet stable strain of Geobacillus sp. WSUCF1, compared with the initial laccase production (0.46 ± 0.04 U/mL) obtained with the unadapted strain grown on unprocessed corn stover before optimization. Chemical composition analysis demonstrated that lignin removal by the adapted strain was 22 wt.% compared with 6 wt.% removal by the unadapted strain. These results signify a favorable prospect for fast, cost competitive bulk production of this thermostable enzyme. Also, this work has practical importance, as this fast adaptation of the Geobacillus sp. strain WSUCF1 suggests the possibility of growing industrial quantities of Geobacillus sp. strain WSUCF1 cells as biocatalysts on reasonably inexpensive carbon sources for commercial use. This work is the first application of the adaptive laboratory evolution approach for developing the desired phenotype of enhanced ligninolytic capability in any microbial strain.
Highlights
Second-generation lignocellulosic plant biomass (LCB) has a global yield of 150 billion tons per year [1], offering an abundant and steady source of renewable organic matter with important potential as an alternative to contemporary starch-based substrates in biorefineries [2]
For laccase production by Geobacillus sp. strain WSUCF1, a 2% (v/v) sample of the seed culture that had been grown at 150 rpm and 60◦C for 48 h was inoculated into 500 mL of the Mineral Basal Salt Solution (MBSS) medium in a 1000-mL flask and incubated at 60◦C and continuous agitation at 150 rpm for 10 days, with the content of the flasks harvested after every 24 h and assayed
Adaptive laboratory evolution (ALE) has appeared as an influential tool in basic microbial research and strain development, where an organism is cultured in a condition of interest for many generations, and fitness is every so often upgraded as beneficial mutations are selected-for and accumulate
Summary
Second-generation lignocellulosic plant biomass (LCB) has a global yield of 150 billion tons per year [1], offering an abundant and steady source of renewable organic matter with important potential as an alternative to contemporary starch-based substrates in biorefineries [2]. Their current usage in a biorefinery is hindered by the complex organic chemistry that exists between the cellulose, hemicellulose, and lignin components of the lignocellulose. Bioprospecting of laccases from thermophiles has garnered particular attention for industrial processes, since bioprocessing of lignocelluloses by laccases at high temperature enables elevated rates of feedstock conversion, attributed to improved enzyme penetration and delignification attained at thermophilic reaction settings [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
