Next generation biofuels: A two-steps prototype for low nitrogen intensive production of oleaginous-microalgae biomass

SANCHEZ-RIZZA L; CURATTI L

Mar del Plata

Congreso; VIII Congreso de Microbiologia General; 2012

Sociedad Argentina de Microbiologia General

Rapid depletion of fossil fuels reserves and concerns over the environment have enormously increased the interest towards research and development of alternative sources of energy. The production of biofuels is one of the technologies that is readily available to start mitigating the global energy crisis and have vigorously emerged lately in the world markets. However, since this first generation of biofuels has posed concerns over competitiveness with food production, land use change and long term sustainability, alternative feedstocks for the next generation of biofuels are actively been investigated. Microalgae are high-producers of oleaginous biomass with great potential to alleviate most of the above mentioned constrains. However, since culture of microlagae is rather high-nitrogen intensive, we are interested to investigate alternatives to improve this aspects towards a mature technology with increased economic competitiveness and environmental sustainability. This work shows a laboratory-scale prototype system for the low-nitrogen intensive production of oleaginous-microalgae biomass in a two-steps cultivation process. The first step consisted in the cultivation of a diazotrofic cyanabacterium and the second step in the bioconversion of this biomass into oil-rich microalgae biomass. From our collection of native cyanobacteria and microalgae a few were selected for these experiments. Both kind of microorganisms were isolated from the region and identified by classical and molecular methods. Data of growth parameters either indoors under controlled conditions or outdoors under environmental conditions and biomass composition were collected for the microorganisms. The selected native cyanabacterium presented remarkable properties of cell sedimentation and flotation that facilitated biomass concentration after culture and ease of preparation of concentrated solutions of proteins, sugars and other soluble cellular components after freezing or desiccation. These preparations were of high nutritional quality and sustained the proliferation of the native eukaryotic oleaginous-microalgae Chlorella sorokiniana strain RP and Scenedesmus obliquus strain C1S without any other amendments. However, both the enzymatic hydrolysis of proteins from bacterial extracts and the addition of diluted mineral medium, allowed a moderate increase in yield. The estimated conversion efficiencies of cyanobacterial proteins into microalga proteins approached 100%. The algal biomass obtained at the expense of bacterial extracts accumulated lipids up to 30 % of its dry weight with no difference in fatty acid profiles, suggesting a conservation of the physicochemical properties of the biodiesel that might be obtained from this feedstock. The results of this work suggest the possibility of technologically coupling complementary metabolic capabilities for the production of oil or other bioproducts from the carbon and nitrogen of the air and light energy. ANPCyT.