Abstract
A rapid expansion of the biodiesel industry has created various ecological issues relative to crude glycerol disposal. Xanthan biosynthesis is considered one of the sustainable solutions for minimizing the adverse effects of waste crude glycerol on the environment. The initial phase of xanthan production on crude glycerol entails the screening of producing microorganism. Therefore, the purpose of this study is to examine the possibility of xanthan production on a crude glycerol-based medium using different Xanthomonas campestris strains. The bioprocesses performed were assessed according to the rheology of the media considered, amounts of xanthan produced and conversion degrees of the most important nutrients present. The pseudoplastic behavior of all the media considered, the amounts of xanthan produced (5.22-7.67 g/L) and the degrees of crude glycerol, total nitrogen and phosphorus conversion (34.44-57.61 %, 23.04-30.35 % and 18.20-22.28 %, respectively) suggest that crude glycerol, after additional bioprocess optimization, can be a suitable raw material for the industrial production of xanthan.
Highlights
Increased global concerns about growing energy demands, limited reserves of fossil fuels and negative impacts of the conventional fossil fuels use on the environment have placed a new emphasis on alternative energy sources
The xanthan production under the experimental conditions was evaluated according to the rheological behavior of the crude glycerol-based media after the cultivation of the Xanthomonas campestris strains considered
The possibility of xanthan production on a crude glycerol-based medium as a sole carbon source using different Xanthomonas campestris strains was confirmed. The efficacy of such production was estimated according to the rheology of the media considered, amounts of xanthan produced and conversion degrees of the most important nutrients present
Summary
Increased global concerns about growing energy demands, limited reserves of fossil fuels and negative impacts of the conventional fossil fuels use on the environment ( greenhouse gas emissions) have placed a new emphasis on alternative energy sources. The biodiesel production involves the utilization of different categories of catalysts such as alkalis, acids, and enzymes. Alkalis and acids are divided into homogeneous and heterogeneous catalysts. Due to their high activity and low costs, sodium hydroxide and potassium hydroxide are the most commonly used catalysts for the transesterification of oils in biodiesel production (Chatzifragkou and Papanikolaou, 2012). Homogeneous base catalysts can be corrosive, and their removal from the resulting biofuel is problematic (often resulting in the formation of stable emulsions and soaps). Heterogeneous catalysis is more efficient as it ensures an easier separation of the catalyst from the final product.
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