Bacillus licheniformis isolated from Mozambican soil capable of producing 2, 3-butanediol
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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.