Sunday, May 3, 2009
6-23
SCREENING OF MICROBIAL FUEL ETHANOL PRODUCERS USING XYLOSE FROM HYDROLYZATE OBTAINED OF DILUTE ACID PRETREATED CASHEW APPLE BAGASSE
Maria Valderez Ponte Rocha1, Ana Laura Tibério de Jesus2, Tiago Lima de Albuquerque2, Vania M.M. Melo3, Gorete de Ribeiro Macedo4, and Luciana R. B. Gonçalves5. (1) Chemical Engineering, Universidade Federal Rural do Semi-Árido, BR 110 - Km 47 Bairro Pres. Costa e Silva, Mossoró, Brazil, (2) Food Engineering, Universidade Federal do Ceará, Av. Mister Hull, Campus do Pici, Fortaleza, Brazil, (3) Biology Departament, Universidade Federal do Ceará, Campus do Pici, Bloco 909, Fortaleza, Brazil, (4) Chemical Engineering, Universidade Federal do Rio Grande do Norte, Av. Sen. Salgado Filho 3000, Natal, Brazil, (5) Chemical Engineering, Universidade Federal do Ceará, Campus do Pici, Bloco 709, Fortaleza, Brazil
The lack of industrially suitable microorganisms for converting biomass into fuel ethanol has traditionally been cited as a major technical roadblock to developing a bioethanol industry. The most widely studied ethanologenic microbes prefer to use glucose as a substrate. Even when yeast cells are modified genetically to use xylose, they ferment all glucose before switching to the much slower xylose fermentation. In the state of Ceará (Northeast of Brazil), the cashew agroindustry has an outstanding role in the local economy and the cashew apple bagasse (CAB) appears as an alternative raw material for ethanol production. The aimed of this work was to screen a number of bacteria and yeasts that can efficiently consumed xylose from CAB. Approximately 78 isolates from this study were tested for growth on xylose as a sole carbon source. Isolates were screened on a MRS modified medium containing xylose as only carbon source and the positive strains were subsequently cultivated in hydrolyzed CAB medium. Three isolates clearly outperformed other strains for rapid growth on xylose as a sole carbon source in MRS. These strains also showed potential to ferment high concentrations of xylose from CAB to produce lactate, acetate and ethanol. Different factors that play an important role in the fermentation were temperature and agitation. One of these isolates was identified as Lactobacillus by NCBI analyses of the 16S rDNA sequence which showed 98% identity with that of L. brevis deposited in the GenBank. These strains present potential applications in CAB biomass conversion for fuel ethanol.