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).