| dc.description.abstract | Due to the current fossil fuel sources rapidly depleting as a result of the increased global need,
alternative, sustainable and renewable sources are required. Biofuels, which are environmentally
friendly, meet all the requirements as they can be generated from the biomass of biodegradable
waste. Selected species of yeast, bacteria and algae are capable of producing biofuels from a host
of substrates. Microorganisms, historically used to manufacture valuable products ranging from
the pharmaceutical to food industry, are now employed to generate biofuels.
Several bacteria are native producers of biofuels and do so without requiring any manipulation.
Some of the most effective biofuel producers are pathogenic organisms, therefore industrialisation
is complicated due to the associated health risks. Generally regarded as safe (GRAS)
microorganisms are preferred vehicles for the production of biofuels as they do not pose any risks
when manufactured at industrial levels. 2, 3-Butanediol (2, 3-BD) was identified as being a
favourable biofuel due its heating value being more favourable than methanol and ethanol. This
compound exists in three stereoisomeric forms and organisms often produce a mixture thereof
depending on the fermentation conditions.
In this study, five bacterial samples isolated from a hot spring were screened for the production of
acetoin, a 2, 3-BD precursor. As mesophilic industrial processes often result in contamination, the
hot spring was an ideal screening environment to by-pass the contamination issue. The isolates
were identified as Bacillus licheniformis with two isolates being closely related to Bacillus
licheniformis ATCC 14580. The B. licheniformis isolate is a GRAS organism known to produce a
mixture of meso and dextro-2, 3-BD at a wide range of temperatures while using several different
substrates and carbon sources. Nutrient broth (NB), Luria Bertani (LB), Beef extract (BE) and
Zymobilis media (ZM), an in-house media, were compared to determine which yielded the highest
growth rate. Based on the literature and the results generated in the comparative analysis, LB was
selected to determine the effect of various carbon sources on the growth rate of the isolates. Unsupplemented
Luria Bertani was compared to LB supplemented with either sucrose, fructose,
starch and glucose. A marked increase in cellular density was detected in the carbon-supplemented
media. High performance liquid chromatography was used to determine the compounds produced
in the glucose-enriched media. We were able to identify 2, 3-BD at 37°C in cultures of all five
isolates. Four of the isolates produced only meso-2, 3-BD, which is significant and of great
industrial importance as no downstream applications would be required to separate the two
isoforms. Further work can be performed to examine production of 2, 3-BD at elevated
temperatures. | en_US |
