Optimization of growth operational conditions for CO2 biofixation by native Synechocystis sp.

BACKGROUND: A fundamental step in assessing the viability of a CO2 biofixation system based on microalgae is to identify the maximum CO2 biofixation yield that can be achieved for this microorganism when it is cultivated under optimum operational growth conditions. Response surface methodology was applied to determine optimum culture conditions for CO2 biofixation by a recently isolated freshwater cyanobacterium Synechocystis sp. The strain was cultivated in a 1 L bubble column photobioreactor, in semicontinuous mode. RESULTS: Statistical analysis showed that temperature (from 22 to 39 degrees C), pH (from 7.2 to 8.8) and light intensity (from 928 to 2272 mu E m(-2) s(-1)), in addition to some of their interactions, had a significant effect on CO2 biofixation. An optimum CO2 biofixation rate of 2.07 gCO(2) L(-1)culture day(-1) was found within the experimental region, at an average light intensity 686 mu E m(-2) s(-1), pH 7.2 and temperature 35.3 degrees C. CONCLUSIONS: Based on these results, it is concluded that Synechocystis sp. presents a good tolerance to both high temperature and light intensity, characteristics which facilitate its application in outdoor CO2 biofixation systems. (C) 2011 Society of Chemical Industry