Effect of Salinity, pH, Light Intensity on Growth and Lipid Production of Microalgae for Bioenergy Application

Abstract

The crisis of energy producing molecules (fuels) is expected to increase in future, which is currently produced from crude mineral oil. Biodiesel is most reliable, non-toxic, biocompatible liquid fuel that can replace the existing unsustainable sources of energy. Among all the known sources, microalgae display high potential for the production of biodiesel owing to their numerous benefits like higher biomass productivities than plants, no agricultural land requirement, cultivation in waste water and accumulation of 20-50% triacylglycerols. Microalgae biomass and lipid content plays an important role in commercial production of biodiesel. The present work was carried out to develop an axenic culture of a potential microalga Chlorella sp. for high biomass and enhanced lipid accumulation. The important growth parameters like pH, light colour, light intensity and photoperiod were studied for better production of Chlorella biomass. The effect of salinity on cell growth was also studied and compared with normal Fogg's medium grown cells. The main biomolecules like carbohydrate, protein, lipid and chlorophyll content were also estimated with the help of standard biochemical methods in salt supplemented and without salt Fogg's medium. The cellular lipid content was increased by growing the cells under different salt concentrations. The micro algal strain showed highest growth of 0.822 g L −1 and 1.021g L −1 in Fogg's medium and under 0.2 M NaCl supplemented medium respectively. However, the maximum lipid production of 0.1842 g L −1 was estimated by growing the cells in Fogg's medium including 0.5 M NaCl with slight compromise in cell growth (0.858 g L −1 ). The lipid content of Chlorella sp. was found to be 26.84% as compared to 14% obtained under normal culture condition. Thus, growing Chlorella sp. under salt supplemented medium and optimizing light requirement will produce high biomass and oil for biodiesel production.

An overview of the utilisation of microalgae biomass derived from nutrient recycling of wet market wastewater and slaughterhouse wastewater

“…The decrease in chlorophyll content is associated with low microalgae activity and the low removal of nutrients from wastewater. Rai et al (2015) revealed that the maximum production of the biomass was recorded at pH 7 (1.3 g L -1…”

“…Microalgae use carbon at low light intensity to synthesise amino acids, whereas under saturated light, the microalgae cells produce sugars, lipids, and starch (Pérez-Pazos and Fernández-Izquierdo 2011). Rai et al (2015) estimated biomass and lipid production under different light and dark periods. The study revealed that the maximum biomass (0.54 g/L) and lipid yield (0.079 g/L) were recorded when microalgae were exposed to light for 24 h, whereas the minimum production amounted to 0.25 and 0.04 g/L for biomass and lipids, respectively, with 8 h of incubation under light.…”

Enhancement of biodiesel production from the green microalga Micractinium reisseri via optimization of cultivation regimes

“…The main role of sodium chloride in algal media may be oxidative stress leading to increment in the triacylglycerol content [28][29][30] and/or changes in lipid amount and composition [27]. The type and concentration of salts are strain-dependent [31].…”

The effect of physicochemical conditions and nutrient sources on maximizing the growth and lipid productivity of green microalgae

“…exposed to green light had an adverse effect on lipid production in comparison with white, yellow, and red light conditions. In this case, the highest cell growth and lipid production (13.10% of its biomass) was under red light (Rai et al ). Kim et al () demonstrated that Scenedesmus sp.…”

“…Moreover, Chlorella sp. showed a higher biomass production under initial pH 7 and the maximum lipid production was found at initial pH 8, comprising 23% of its biomass (Rai et al ).…”