Heterologous expression of LamA gene encoded endo-β-1,3-glucanase and CO2 fixation by bioengineered Synechococcus sp PCC 7002

The gene for the catalytic domain of thermostable endo-beta-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 degrees C. At a CO2 concentration of 5%, we obtained a maximum specific growth rate of 0.083 h(-1), a biomass productivity of 0.42 g.L-1.d (-1), a biomass concentration of 3.697 g.L-1, and a specific enzyme activity of the mutant strain of 4.325 U.mg(-1) 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-1.d(-1)), biomass concentration (2.416 g.L-1), and specific enzyme activity (3.247 U.mg(-1) dry mass). (C) Higher Education Press and Springer-Verlag Berlin Heidelberg 2017