Anaerobic ethanol production using bran as a substrate
Date
2020
Authors
Momoniat, Muniera
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Abstract
Biofuels have been exploited as a substitute for non-renewable fossil fuels by
humankind for several decades. The source has been mainly plants that are also
used to make other important economic products. It is therefore important to
investigate other less costly methods of producing this important environmentally
friendly fuel. The purpose and focus of this research were threefold; to isolate a
thermophilic and mesophilic (control) mixed bacterial consortium that degrades
lignocellulose efficiently and produces ethanol, to run an anaerobic fluidised bed
bioreactor (AFBR) that produces ethanol and to use molecular methods to identify
the bacterial species making up the consortia. Winogradsky columns were used as
enrichment culture, and a microaerophilic culture technique was employed to
isolate cultures that took from 5 days for complete filter paper degradation
(mesophilic and thermophilic). Thermophilic and mesophilic bacterial consortia
were constructed from a few of the fastest degrading cultures. The mesophilic
consortium isolated was run in an AFBR. The thermophilic consortium (65°C) was
obtained from freshly collected elephant, impala, eland and kudu dung collected at
the Johannesburg zoo was mixed and inoculated into endo medium and incubated
at 65°C. The AFBR was optimised and operated under mesophilic and thermophilic
conditions by obtaining a steady reduction in the settled bed volume, indicating
cellulolytic degradation of the fluidised bran bed and ethanol production. The
population structure of the bacterial consortia was determined using molecular
techniques: polymerase chain reaction amplification of ribosomal rDNA using
universal markers and DGGE was used to separate species into separate bands
(species), indicating the similarity and differences in the population structures in
the thermophilic, mesophilic and reactor samples. The result of this study show
that the Winogradsky column as well as termites can be exploited as a source
bacteria consortia for ethanol production
Description
A dissertation submitted in fulfilment of the requirements for the degree of Master of Science
in Molecular and Cell Biology in the Faculty of Science, University of the Witwatersrand, Johannesburg, 2020