The Impact of Combined Alkalinity and Time Pretreatments on Light- harvesting System in Tresterial Cyanobacterium Fischerella sp. FS 18 (Oscillatorials, Cyanophyta)

Possibility of change in the phycobili-some status, photosynthetic pigments, pho-tosynthetic ratios, and photosynthetic pa-rameters of soil cyanobacteria Fischerella sp. FS 18 investigated. Neutral and extreme alkaline pH (7, 9), and short time incubation including 20, 40, and 60 minutes treatments. After purification, cyanobacteria were sub-jected to extreme alkaline treatment for one hour at 20, 40, and 60 minutes intervals. Colorimetric assays of phycocyanin, allo-phycocyanin, phycoerythrin, chlorophyll) and a comparison of the combined effect of time and alkalinity on photosynthetic ratio performed. Indeed, the photosynthesis-light curves compared with direct measurements. The results showed that the combined treat-ment of time and alkalinity after 20 minutes of inoculation significantly increased the performance of the photosystem and stability of the phycobilins. While, under the 40 min and both neutral and alkaline treatments, the yield of photosystem II, in-creased the production of thephotosystem I, and significantly the linear fraction of the photosynthesis-light curve. Although, the needed energy to achieve maximum pho-tosynthesis reduced. Further, the maximum photosynthesis was completely different at 40 min pretreatmentand without pretreat-ment. Furthermore, the results show no spe-cific regularity and trend at20 and 60 min-utes times treatment. Thus, the production of light collecting-antennas is influenced by both time and alkalinity treatments. In con-sequent, 60 minutes or less treatment times, cause a significant change in the structure and performance of the photosynthetic ap-paratus. While, alkaline treatments at a short time significantly save energy and enhance photosynthesis.