Boris Ugarte Stambuk
Dr. Boris U. Stambuk is Full Professor of Biochemistry at the Federal University of Santa Catarina (UFSC), in Florianópolis, SC. He earned a M.S. in Microbiology and Immunology from Federal University of São Paulo (1991), and a Ph.D. in Biochemistry from University of São Paulo in 1997. He was senior research associate at the National Renewable Energy Laboratory in Golden, CO (2001-2002), and visiting professor at the Department of Genetics, Stanford University School of Medicine, CA (2006-2007). Dr. Stambuk is professor at the Graduate Program in Biotechnology and Biosciences, and Graduate Program in Biochemistry, both at UFSC. His Yeast Molecular Biology and Biotechnology Laboratory focusses on sugar transport and fermentation by yeasts, both for the brewing and biofuels industries, having published over 60 articles in the field. His research focusses in the genomic analysis of fermentative and industrial yeasts for further optimization, metabolic (and evolutionary) engineering, and discovery of new species, genes and proteins/enzymes useful for second-generation bioethanol production.
Cloning new sugar transporters and enzymes for second-generation bioethanol production by recombinant S. cerevisiae
Lignocellulosic biomass is an attractive raw material for bioethanol production, and abundant research has been devoted to improve xylose and cellobiose utilization by recombinant S. cerevisiae strains. We have cloned and expressed in this yeast novel xylose reductases (accepting both NADH and NADPH co-substrates) and xylitol dehydrogenases from Spathaspora yeasts isolated in Brazil. Since limited uptake is one of the bottlenecks for xylose fermentation, we also aimed to identify novel sugar transporters from the xylose-fermenting yeasts for expression in an hxt-null S. cerevisiae strain, lacking the major hexose transporters (hxt1D-hxt7D and gal2D) but having high xylose reductase, xylitol dehydrogenase and xylulokinase activities. Five genes allowed xylose and glucose consumption by the recombinant strain: the SUT1 permease from S. passalidarum, the SUT2 permease from S. arborariae, and three genes from S. stipitis (XUT1, HXT2.6 and QUP2). Other genes from S. arborariae or S. passalidarum failed to consume all sugars tested. Thus, we undertook a novel approach cloning the transporters but removing sequences from the N- or C-terminal intracellular domains. The truncated version of the transporters allowed glucose and xylose fermentation. Finally, novel cellobiose transporters and intracellular β‑glucosidases cloned from S. passalidarum allowed efficient cellobiose fermentation by recombinant S. cerevisiae cells. We will also address the development of recombinant industrial yeasts used in Brazil for second-generation bioethanol production from sugarcane.
Financial support: CNPq, CAPES, FINEP and FAPESC.