Improving the photosynthetic productivity and light utilization in algal biofuel systems: Metabolic and physiological characterization of a potentially advantageous mutant of chlamydomonas reinhardtii

In this study, we report initial biophysical and biochemical characterization of a spontaneous ‘mutant’ (referred to as ‘IM’) of the green alga Chlamydomonas reinhardtii with several unique attributes that has potential for improving photosynthetic productivity, light utilization efficiency, and, perhaps, even protection against environmental stress. Growth rate experiments showed that under low light intensity (10 μmol photons m⁻² s⁻¹), IM showed 36% higher cell density and 25% higher dry cell weight than the wild type cells (WT), while at higher light intensity (640 umol photons m⁻² s⁻¹ ), the IM did not show any advantage. Chlorophyll a fluorescence transient measurements and subsequent analysis indicated that IM cells grown at a light intensity of 20 μmol photons m⁻² s⁻¹ had a higher light utilization efficiency in comparison to the WT cells. Interestingly, metabolite profiling analysis showed that during the exponential growth phase with both low and high light intensities (10 and 640 umol photons m⁻² s⁻¹), the IM cells had higher concentrations than WT cells for several important metabolites that have been previously shown to help protect against environmental stress.