Ethanol production using Saccharomyces cerevisiae cells immobilised on corn stem ground tissue

Abstract

Cell immobilisation in alcoholic fermentation has been extensively studied during the past few decades because of its technical and economical advantages over those of free cell systems. A biocatalyst was prepared by immobilising a commercial Saccharomyces cerevisiae strain (baker yeast) on corn stem ground tissue for use in alcoholic fermentation. For this purpose, the yeast cells were submitted to the batch tests 'in situ' adsorption onto pieces of the corn stem ground tissue. Cells immobilisation was analysed by optical microscopy. It was determined that the addition of the corn stem ground tissue led to an increase of the pH value, total dissolved salts content, and sugar content in fermentation medium. The addition of 5 and 10g of the corn stem ground tissue per liter of medium, increased ethanol yield, decreased amount of residual sugar and the cells immobilisation was effective. Corn stem is one of the abundant, available, inexpensive, stable, reusable, nontoxic celulosic biomaterial with high porosity, which facilitates the transmission of substrates and products between carrier and medium. The prepared immobilised biocatalyst showed higher fermentation activity than free cells. The results indicate that corn stem might be an interesting support for yeast cell immobilisation, and also a cheap alternative recourse of mineral components with possibility of application for improving ethanol productivities.Primena imobilisanih celija u alkoholnoj fermentaciji je veoma aktuelna istrazivacka tematika, usled mnogobrojnih tehnickih i ekonomskih prednosti u odnosu na fermentaciju pomocu slobodnih celija. U ovom radu je ispitana mogucnost primene imobilisanih celija kvasca Saccharomyces cerevisiae na parenhimskom tkivu kukuruzovine, u alkoholnoj fermentaciji. Proces imobilizacije celija pracen je optickim mikroskopiranjem i merenjem suve materije imobilisanog kvasca. Ustanovljeno je da dodatkom nosaca u fermentacionu podlogu raste pH vrednost, kao i sadrzaj soli i secera usled ekstrakcije ovih komponenata iz kukuruzovine. Dodatkom stabljike kukuruza u kolicini 5 g i 10 g na litar podloge za fermentaciju ostvaruju se visi prinosi etanola, visok stepen konverzije secera, veca brzina fermentacije, postize se visok stepen imobilizacije celija kvasca. Stabljika kukuruza je raspoloziv, jeftin, stabilan, ponovno upotrebljiv, netoksican i mehanicki stabilan celulozni biomaterijal visokog stepena poroziteta koji olaksava prenos mase supstrata i produkata izmedju medijuma i nosaca. Rezultati ovog rada ukazuju na cinjenicu da je stabljika kukuruza efikasan nosac za imobilizaciju celija kvasca, ali takodje i dodatni izvor hranjivih materija neophodnih kvascu tokom fermentacije, cija je primena u proizvodnji etanola ekonomski i ekoloski opravdana.