Use of discards of bovine bone, yeast and carrots for producing

Abstract

The reutilization of agroindustrial wastes for the production of new products is an attractiveoption for reducing environmental pollution, generating value-added products anddecreasing costs. Slaughterhouse discard bovine bone, brewery discard yeast and carrotdiscards from the Santa Fe province (Argentina) were used for producing ethanol. Bovinebone and yeast provided the support and active phase for fermentation biocatalysts whilecarrot discards were a sugar source. Discard bovine bone was collected directly from aslaughterhouse and then subjected to extraction with acetone for removing lipids and bloodtraces. Both uncalcined and heat-treated bovine bone (calcined for 2 h at 400, 600 and800°C) were studied. Uncalcined bovine bone had a suitable pore structure for yeastimmobilization and a suitable mechanical resistance for being used in stirred tanks.Two different strains of Saccharomyces cerevisiae were immobilized and tested. One wasa brewery yeast discarded from a local beer brewery and the other one a commercial yeast.The biocatalysts thus obtained were subjected to a thermal treatment at 35 ºC for 72 h inorder to dehydrate cells and form adhesins. The activity of the biocatalysts was tested inthe fermentation of carrot discards. The maximum concentration of the obtained ethanolwas 11.98 g L-1. It was possible to reuse the biocatalysts for 9 reaction cycles. Thepossibility of regenerating the biocatalyst bone support by ultrasound is an advantage ofthis kind of material in comparison to common gel supports.