Abstract
Production of microalgae as feedstock for biofuels must deal with a number of challenges including constraints imposed by local conditions. One solution is to use indigenous strains adapted to local climatic conditions. The present report describes the isolation, identification, and characterization of 32 microalgal strains from different ecological habitats: desert freshwater channels, northern region, and saline regions of Pakistan. The effects of temperature on algal growth rates, biomass productivity, and lipid content were determined through growth at 12, 20, and 35 °C for 15 days under 2% CO2 Responses to temperature varied among species with 20 °C being the optimum temperature in general, although, exceptionally, the best overall growth rate was found for strain S29 (0.311 d−1) at 12 °C. In some cases high biomass productivity was observed at 35 °C, and, depending upon the strain, the maximum lipid content was obtained at different temperatures, including 12 °C. Fatty acid methyl ester (FAME) analysis showed that the major fatty acids present were palmitic, stearic, oleic, linoleic, and linolenic. Oleic acid (C18:1) was the predominant fatty acid, with the specific FAME profile varying with strain. Thus, there is a rich diversity of microalgal strains native to Pakistan, some of which, characterized here, could be suitable for biodiesel production or other biotechnological applications.
Highlights
In addition to characterizing individual strains as to their growth response to different temperatures, these results suggest that there is a great deal of diversity of responses, even within a relatively small sample of microalgal strains
Thirty-twoindigenous indigenousstrains strainsofofgreen greenalgae algaewere wereisolated isolatedfrom fromdisparate disparateareas areasofofPakistan, Pakistan, identified, and characterized. They were examined for growth rate, biomass production, lipid identified, and characterized
They were examined for growth rate, biomass production,and and lipid
Summary
Microalgae are being intensively investigated due to their rapid growth and variety of potential applications, in particular as promising feedstocks for biofuel production [1,2,3,4], biogas production [5,6], wastewater purification [7,8], and animal feed [9], as well as for human food and nutraceutical products [10].The necessity for developing sustainable sources of energy has become obvious as non-renewable conventional energy extraction and use (petroleum, oil, natural gas, and coal) have already caused worldwide climatic changes [1,11]. Microalgal characteristics that are favorable for this type of process include: short generation times, high lipid content, cost effective nutrient sources, the capacity to develop in assorted natural surroundings with different types of wastewater, and higher photosynthetic capability compared to terrestrial energy crop plants [7,13,14]. Microalgal growth and productivity are strongly influenced by biotic and abiotic environmental factors. Algal biomass productivity is the net consequence of photosynthesis, which is strongly influenced by both temperature and light [15,16]. Microalgae have the potential to accumulate as much as 30%–70% of their cellular dry weight as lipid under various conditions [7]. One of the key factors that can potentially influence cellular lipid accumulation is temperature [16,17]. The adaptability of microalgae to different temperature regimes is species dependent and the prospective biotechnological applications of thermophilic (>50 ◦ C) or even mesophilic (30–50 ◦ C) microalgae are only poorly developed
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