Journal of Environmental Chemical Engineering 2 (2014) 1294–1300 Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j e c e Biodiesel production from marine microalga Chlorella salina using whole cell yeast immobilized on sugarcane bagasse Duraiarasan Surendhiran * , Mani Vijay, Abdul Razack Sirajunnisa Bioelectrochemical Laboratory, Department of Chemical Engineering, Annamalai University, Annamalainagar, Tamil Nadu 608002, India a r t i c l e i n f o Article history: Received 20 January 2014 Accepted 7 May 2014 Keywords: Chlorella salina Biodiesel Methyl acetate Whole cell biocatalyst Interesterification a b s t r a c t Nowadays microalgae have become a potential source for production of biodiesel due to its fast growth rate, high lipid content and incapable of affecting the food chain. In this study immobilized whole cell yeast Rhodotorula mucilaginosa MTCC8737 was employed for conversion of marine microalga Chlorella salina oil into biodiesel by non-alcoholic route in a solvent-free system. Various parameters were evaluated to enhance the biodiesel yield with methyl acetate as an acyl acceptor. The maximum biodiesel yield was obtained at 85.29% with the optimum conditions of 1.5 g whole cell biocatalyst, 1:12 methyl acetate to oil ratio, 10% water content (w/w), temperature of 40 ◦ C, 60 h of reaction time and agitation at 250 rpm. The stability of immobilized whole cell biocatalyst was studied with 10 cycles of repeated usage and it was shown that there was no significant loss of lipase activity in the presence of methyl acetate. The fatty acid composition was analyzed by gas chromatography, which resulted that palmitic (C16:0) and oleic acid (C18:1) are predominant in C. salina biodiesel. This study proved that the use of whole cell yeast immobilized on sugarcane bagasse is cost-effective, ecofriendly and an alternative method for enzymatic biodiesel production on a commercial scale. c  2014 Elsevier Ltd. All rights reserved. Introduction Currently there is a worldwide interest in finding out new alter- native fuels against fossil fuels because of diminishing and over con- sumption of hydrocarbons which, result in the accumulation of green house gases in atmosphere that ultimately leads to global warming [1,2]. Biodiesel (monoalkyl esters of long chain fatty acids) is a po- tential renewable biofuel and it is biodegradable, non-toxic, has no net carbon dioxide and is free of sulfur [3–6]. Generally, biodiesel is produced from food materials and oil crops using conventional meth- ods [7]; however these sources cannot realistically replace the wide use of diesel fuel due to increasing demand. Also the over population worldwide has lead to serious land shortage and raised the issue of food security [8]. Microalgae have become a recent attraction because of high oil content, and can be grown in wastewater as they do not compete with food crops for arable land and water and give 20 times more biomass productivity rate than the terrestrial crops [9–14]. Mi- croalgae are photosynthetic microorganisms that utilize light, water and CO 2 and accumulate intracellular lipids as storage materials [15]. Currently biodiesel is being produced employing conventional methods such as acid and alkali transesterification that results in the conversion of triglycerides into fatty acid methyl esters in a shorter period [16,17]. Major drawbacks of conventional methods include high energy input, elimination of salt, difficulty in recycling glycerol, * Corresponding author. E-mail address: suren micro@yahoo.co.in (D. Surendhiran). soap formation and requiring wastewater treatment [18–25]. To over- come these problems, enzymatic production of biodiesel has recently become an alternative for biodiesel production because the byprod- uct glycerol can be easily recovered, salt and catalyst can be avoided, wastewater treatment is not required, high production yield could be attained under milder conditions and it is an ecofriendly process [26–28]. One such enzymes used in biodiesel production are lipases. Lipases (triacylglycerol acylhydrolase, EC 3.1.1.3) are produced by mi- croorganisms, plants and animals, but for the large scale production microorganisms are more suitable [29]. However, the enzymatic production of biodiesel is not yet com- mercialized due to high cost involvement in the isolation, purification, and immobilization on a carrier as well as to low stability of lipase in methanol [30–33]. To overcome these problems, we have focused on whole cell biocatalyst for biodiesel production, i.e. microorganisms, which contain lipase intracellularly or in their cell wall. The advan- tages of whole cell biocatalyst include inexpensive process, recycla- bility of biocatalyst, no purification process, stability to methanol and low production cost [15,18,25]. Nowadays, the enzymatic synthesis of biodiesel in solvent free system is focused globally, because such systems are advantageous over solvent aided transesterification by avoiding separation, toxicity, flammability and high cost of organic solvents [20,33]. In this work, biodiesel had been produced by interesterification of oil from microalga, Chlorella salina. Biocatalysis of the reaction was performed by whole cells of Rhodotorula mucilaginosa producing li- pase which was immobilized on an agro waste, sugarcane bagasse. As 2213-3437/$ - see front matter c  2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jece.2014.05.004