Effect of Salinity and pH Control on Carbohydrate Analysis of Cyanothece BG0011

Algae are largely being explored for their ability to produce high quantities of carbohydrates or lipids, which can subsequently be used to produce renewable fuels, along with other valuable biochemical products. They are an attractive option as a source for alternative fuels as they do not compete for agricultural resources, cultivate high biomass per growth area, and are able to decrease greenhouse gas emissions. The marine microalgae strain Cyanothece BG0011 possesses attractive characteristics, such as being able to fix nitrogen from the ambient air, being able to grow under harsh living conditions, and the ability to produce large quantities of extracellular polymeric substances (EPS). In this study, the effect of salinity, including hypersaline conditions, at a two pH values was investigated. Sixteen 200-mL photobioreactors were set up and operated for 42 days. They were divided into four groups containing four bioreactors each. One group was at a salinity of 26 ppt and pH of 7.25±0.25, the second group at a salinity of 26 ppt and pH 8.5±0.2, the third group at a salinity of 50 ppt and pH of 7.25±0.25, and the fourth group at a salinity of 50 ppt and a pH of 8.5±0.2 (The salinity of seawater is 33-38 ppt). Total carbohydrate analysis was performed each week on the supernatant from each of the reactors and on the EPS at the end of the run time. The weekly analyses showed that the average carbohydrate concentration was highest at 50 ppt and pH 8.5, and lowest at 26 ppt and pH 7.25. If the objective is high carbohydrate production, hypersaline alkaline conditions are optimal.