Literature Review On Microalgae

Microalgae is considered as one of the promising sources of energy production but it is still not economically viable and environmental impact. In the past years, various factors in cultivating microalgae indoor and outdoor were identified. One of the major drawbacks limiting the cultivation of microalgae outdoors in open ponds is low productivity and contamination. Limited light availability in the deeper layers of the ponds to the cells (Goldman, 1979); photo inhibition in the summer caused by high light intensity in the upper layer of the pond (Powles, 1984); above optimal day temperatures in the summer and suboptimal temperatures in the winter (Richmond 1986); also increased respiration and hence loss of biomass caused by high night temperatures

1984, Photoinhibition of photosynthesis induced by visible light. Ann. Rev. Plant Physiol. 35: 15-44
Richmond A. 1986. Hndbook of Microalgal Mass Culture, CRC Press.
Richmond, A.E. 1986. Microalgaculture. CRC Crticial Reviews in Biotechnol. 4: 369-438. http://onlinelibrary.wiley.com/doi/10.1002/elsc.200800111/pdf 2.LITERATURE REVIEW
2.1.Growth requirements and design parameters:
In achieving economic and environmental feasible production of microalgae the most important factor is developing cost-effective, sustainable culture systems (Borowitzka, 1999; Richmond, 2000). The key to achieving economic viability is improving productivity In outdoor cultures (Lee, 2001). In order to achieve optimal microlagal growth, parameters such as temperature, light intensity, pH and nutrient concentrations must be kept under consideration

Borowitzka, M. A. (1999). Commercial production of microalgae: ponds, tanks, tubes and fermenters. Journal of biotechnology, 70(1), 313-321.
Richmond, A. (2000). Microalgal biotechnology at the turn of the millennium: a personal view. Journal of Applied Phycology, 12(3), 441-451.
Lee, Y. K. (2001). Microalgal mass culture systems and methods: their limitation and potential. Journal of applied phycology, 13(4), 307-315.

For mass cultivation of microalgae, ammonia, urea and nitrate are selected as nitrogen source. Due to its low cost, ammonia and urea are used in cultivation, however, urea and nitrate were found to be better nutrients than ammonia for growth and lipid accumulation (Li et al. 2008b; Hsieh and Wu 2009). When microalgae are cultivates under stress conditions like nitrogen starvation, nutrient deficiency, pH variations etc, reports suggest that nitrogen starvation conditions increases oil/ lipid content (Mandal and Mallick, 2009).Although this strategy is efficient in increasing lipid content of microalgae, the nitrogen deficiency conditions lead to decrease in growth of microalgae rate, thereby causing negative impact on lipid productivity.Microalgal biomass and lipid productivity can be enhanced through phosphorous starvation as reported for Monodus subterraneus ((Khozin-Goldberg and Cohen, 2006) while the fatty acid composition changes for Phaeodactylum tricornutum and Dunialella tertiolecta (Siron et al.,