Natural Resources, 2014, 5, 5-9 Published Online January 2014 (http://www.scirp.org/journal/nr ) http://dx.doi.org/10.4236/nr.2014.51002 5 Osmotic Stress Effect over Carbohydrate Production in a Native Starin of Scenedesmus sp. Pilar Bremauntz 1* , Luis C. Fernández-Linares 1 , Rosa O. Cañizares-Villanueva 2 1 Laboratory of Bioprocesses, Department of Bioprocesses, Unidad Profesional Interdisciplinaria de Biotecnología (UPIBI), Instituto Politécnico Nacional, México, D.F., México; 2 Departamento de Biotecnología y Bioingeniería, Centro de Investigación y de Estudios Avanzados, Instituto Politécnico Nacional, México, D.F., México. Email: * pilarbrem@yahoo.com.mx Received November 11 th , 2013; revised December 9 th , 2013; accepted December 30 th , 2013 Copyright © 2014 Pilar Bremauntz et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In accor- dance of the Creative Commons Attribution License all Copyrights © 2014 are reserved for SCIRP and the owner of the intellectual property Pilar Bremauntz et al. All Copyright © 2014 are guarded by law and by SCIRP as a guardian. ABSTRACT The production of biofuels is currently presented as a possible answer in the search for sustainable alternatives for the total or partial substitution of fossil fuels. One of the most successful biofuels that have been developed is bioethanol. However, bioethanol production has been limited since it relies on the use of sugar cane or cereals. These materials are important sources of food and their demand as both a biofuel and a foodstuff has led to the price increase and may lead to possible shortages. Our group has focused on searching for native microalgae as sources of carbohydrates and bioethanol, with the goal of finding a sustainable source of bioethanol. Currently, twelve different strains which reach growth rates between 0.7 - 1.8 g/L and present carbohydrate production under osmotic shock conditions have been isolated. In this work, we demonstrate the results obtained with the Chlorella sp. [1] strain and the results obtained with the Scenedesmus sp. strain. The Scenedesmus sp. strain showed an increase in the production from 22 to 650 mg/sugar/g of biomass (dry weight), after 24 hours of os- motic shock with 0.1 M NaCl. The osmolytes which were produced after osmotic shock were identified as sucrose and trehalose, both of which are fermentable. These results demonstrate that this strain, through the photosyn- thetic pathway and osmotic shock, is a potential source of fermentable sugars. KEYWORDS Biofuels; Bioethanol; Microalgae; Scenedesmus sp.; Carbohydrates 1. Introduction Microalgae are oxygenic photosynthetic organisms that are found in diverse environments such as salt water and fresh water. They are even found in environments as ex- treme as desserts. The majority of these organisms are photosynthetic species, as such they are capable of pro- ducing sugars from CO 2 and light [2-4]. Sugar produc- tion in these algae has been shown to increase as a re- sponse to osmotic shock generated by high salt concen- trations, a mechanism known as osmoregulation [5,6]. Much is known about the large quantity of compounds that the algae produces as osmoregulators. These com- pounds range from simple carbohydrates to amino acids and even complex compounds such as digenosides [7,8]. Some of these osmoregulators synthesized by algae can have commercial uses. This is the case for glucose, sucrose, and trehalose which can even be fermented to produce bioethanol [1]. The production of bioethanol is a technology that has been established in countries like Brazil and the United States [9], and usually is obtained from either the fer- mentation of starch from different materials such as wheat or direct fermentation of carbohydrates using sug- ar cane or even from lignocellulose residues [10]. How- ever, the production of bioethanol from primary sources that are food is not sustainable due to inevitable competi- tion with human consumption. Hence, the production of bioethanol from microalgae biomass could be an attract- * Corresponding author. OPEN ACCESS NR