Isolation and Characterization of Yeast from Sisal Boles for Bioethanol Production

Abstract

Sisal boles are part of the 98% sisal plant waste that is discarded. They have a high bio-diversity of microorganism species, including yeast that can be utilized for bioethanol production. The objective of the study was to isolate yeast cells from sisal boles juice for bioethanol production. Sisal boles for juice extraction were randomly collected from Ubena sisal estate, Pwani region. To preserve the targeted microorganisms cold juice pressing method was used. Pour plate method was used on Potato Dextrose Agar and four distinct colonies were formed and repeatedly sub-cultured to obtain four pure yeast isolates. The juice yield was only 510 mL per kg of sisal bole, which is below the yield for autoclaved sisal bole obtained by other researchers. The yeast identified was concluded to be Saccharomyces cerevisiae based on the macroscopic and microscopic morphological observations. Isolated S. cerevisiae is better conditioned for fermentation of sisal bole juice to various products, including bioethanol. Upon the fermentation and temperature tolerance test, all the indigenous yeast isolates could ferment glucose, sucrose, maltose and fructose and tolerate incubation temperatures up to 45ºC. Therefore, the indigenous S. cerevisiae isolates can reliably be conditioned for use in ethanol production using sisal wastes.