Development of bioprocess for the production of microbial and algae lipids from starch tubers

Abstract

Abstract: Facing the problem of increasing energy demand, feasible fossil fuels substitutes have been studied. Some microbial strains are capable to accumulate large quantities of lipids also known as oleaginous microorganisms can use converted (into glucose) starch from cassava to lipid production that can be transesterificated to good quality biodiesel. The knowledge of starch content in amylaceous matter is very important once this residue can be used in further several industrial applications being a high value-added material. Cassava (Manihot esculenta) starchy fractions from integral flour and bagasse were submitted to starch content evaluation, acid hydrolysis optimization, thermal analyses and optical microscopy. The results reveals high good quality starch content in both studied materials. After that, in order we carried out a screening to select a potential biomass/lipid producer from seven different yeast strains using glucose from cassava hydrolysate. After a first selection, where strain A (LPB0035) presented better results a Plackett Burman planning was applied to identify factors presence that influence the lipid production yielding positively and KH2PO4, MgSO4.7H2O, FeSO4, CaCl2, urea and yeast extract were determined. Finally, a 23-factorial central composite design (23-CCRD) was used to evaluate optimum parameter levels for the production based on significative factors observed in previous screening and following concentrations were established (g/L): KH2PO4 (0,5), MgSO4(0,30), CaCl2(0,30) and urea (1,77). After testing process parameters, we found that R. toruloides LPB 0035 was capable to accumulate up to 56,7% (w/w) oil from hydrolysate of cassava tuber and its cell dry weight reached 44,3 g/L at the end of fed batch cultivation. Most of fatty acids obtained from R. toruloides LPB 0035 and C. vulgaris LPB 0033 were C16:0, C18:1 and C18:2. Finally, effluent from batch fermentation presented high biochemical demand oxygen (BOD) and chemical demand of oxygen (COD) values and was submitted to microalgae cultivation in order to reduce pollutants concentrations. Thus, after 17 days of cultivation using C. vulgaris LPB 0033 the final broth achieved more than 50% for both BOD and COD reductions. Biodiesel produced using studied process present suitable characteristics for official international biodiesel specifications.