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Frontiers of Environmental Science & Engineering >> 2017, Volume 11, Issue 2 doi: 10.1007/s11783-017-0910-1

Heterologous expression of

. School of Water Resources and Environment, China University of Geosciences, Beijing 100083, China.. Department of Chemical and Biological Engineering, University of British Columbia, Vancouve, V6T 1Z3, Canada.. Department of Biochemistry and Microbiology, University of Victoria, Victoria, V5Z 4H4, Canada

Available online: 2017-03-17

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Abstract

Maximum growth rate of mutant was 0.083 h with 5% CO . Maximum biomass concentration of mutant was 3.697 g·L . mutant can tolerate gas aeration with 15% CO . Maximum specific activity of laminarinase was 4.325 U·mg dry mass. Optimal pH and temperature of laminarinase activity were 8.0 and 70°C. The gene for the catalytic domain of thermostable endo-β-1,3-glucanase (laminarinase) LamA was cloned from Thermotoga maritima MSB8 and heterologously expressed in a bioengineered Synechococcus sp. PCC 7002. The mutant strain was cultured in a photobioreactor to assess biomass yield, recombinant laminarinase activity, and CO2 uptake. The maximum enzyme activity was observed at a pH of 8.0 and a temperature of 70°C. At a CO2 concentration of 5%, we obtained a maximum specific growth rate of 0.083 h , a biomass productivity of 0.42 g·L ·d , a biomass concentration of 3.697 g·L , and a specific enzyme activity of the mutant strain of 4.325 U·mg dry mass. All parameters decreased as CO2 concentration increased from 5% to 10% and further to 15% CO2, except enzyme activity, which increased from 5% to 10% CO2. However, the mutant culture still grew at 15% CO2 concentration, as reflected by the biomass productivity (0.26 g·L ·d ), biomass concentration (2.416 g·L ), and specific enzyme activity (3.247 U·mg dry mass).

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