| dc.description.abstract | An increase in global demands for fuel from renewable sources has accelerated research into alternative energy sources that are economical and can reduce greenhouse gases. These renewable fuels must also not cause further challenges by competing for agricultural land use with food sources. Therefore, lignocellulosic feedstock, which are cheap and abundant non-food materials are an emerging solution. Concurrently, there is also rising interest in sustainable and renewable based chemicals. Lactic acid is valuable in many industries and is one such chemical. In addition to use as a preservative and emulsifying agent, lactic acid is also a precursor for poly-lactic acid, a biodegradable and biocompatible polymer. Microbial fermentation with Beta vulgaris (sugar beet) in a low-technology process such as ensiling has the potential to provide high titers of ethanol for use as a biofuel and lactic acid for industry. In this project, the utilisation of seven carbohydrates, sucrose, glucose, fructose, xylose, arabinose, cellobiose and D-galacturonic acid by several lactic acid bacteria that were considered potential inoculants for sugar beet ensiling was assessed. This was used to determine the optimal microbial consortia for use as an inoculant to produce high lactic acid yields. A laboratory sugar beet ensiling protocol was also developed and various factors including shredding sugar beet hypocotyls prior to ensiling, incubation between 32-37 °C, 5-7% w/v CaCO3 and 5% w/v sodium chloride determined to produce 20-25 mmol g-1 lactic acid. Ensiling with Saccharomyces cerevisiae, acid and the antibiotic Lactrol resulted in high ethanol selectivity and yields. Lastly, metagenomic analysis of sugar beet samples prior and post ensiling determined the endogenous microbial community and changes to relative distributions during ensiling. Analysis showed Carnobacterium was the most abundant genus and most likely responsible for lactic acid production and sugar beet samples prior to ensiling had greater bacterial diversity than post-ensiled samples. Performing ensiling at optimal conditions with selected additive resulted in high titers of the desired product and reduced by-product formation demonstrating Beta vulgaris can be successfully ensiled. | en_GB |
