CONSTRUCTION OF A S. CEREVISIAE STRAIN FOR THE BIOREMEDIATION OF DAIRY INDUSTRY WASTE COUPLED WITH ETHANOL PRODUCTION

ZUBAK, TOMAS A.; CASSAIN, SANTIAGO J.; D'ALESSIO, CECILIA

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB conference en Salta; 2019

SAIB

The dairy industry is an integral part of thefood industry, being one of the largest, most important and dynamic agro-foodcomplexes within the national economy. This industrial segment producesconsiderable amounts of liquid waste with a high content of organic matter.Whey is the remaining liquid from the precipitation and removal of casein frommilk during the cheese manufacturing process. It is made up of severalcomponents, with lactose being the most abundant (4.5 - 5% w/v). This sugarcontributes to the high chemical oxygen demand and biochemical oxygen demand ofwhey. Bioethanol may be obtained from various compounds by microorganisms as yeasts,which have the ability to ferment a wide variety of sugars to alcohols. Yeasts areused in industrial plants because of their great fermentation yield, ethanoltolerance, productivity and their efficient growth in simple and economicalmedia. Thus, the use of whey for the production of ethanol from thefermentation of lactose would be a beneficial process due to the reuse andbioremediation of this highly polluting by-product. By integrating the genesLAC4 and LAC12 from Kluyveromycesmarxinaus to the genome of the Saccharomycescerevisiae laboratory strain BY4742,we have developed several transgenic strains capable of using lactose as a solecarbon source. Using a spectroscopy technique we determined the ability of thesestrains to produce bioethanol both from sucrose and lactose and compared it toa wild type Saccharomyces cerevisiae strain.Our results show that while wild type S.cerevisiae strain is not capable of growing even in rich mediums if theycontain lactose as the sole carbon source, the engineered strains are able toefficiently catabolize lactose into bioethanol in anaerobic conditions. Two ofthe strains obtained, BY4742-11F and BY4742-51, were able to produce a finalconcentration of 1.1% and 0.74% ethanol from a 2% lactose rich medium, valuesclose to the maximum theoretical yield. These promising results justify furtherstudies leading to an optimization in the production of bioethanol from this foodprocessing waste using the strains obtained