Modelling and operation of reactors for enzymatic biodiesel production

In developing sustainable industrial processes, biochemical engineering, as a part of a
broader field of chemical engineering is becoming an increasingly important as a tool in the
chemical engineers toolbox. Its application is driven by consumer demand for new products
and by industry wishing to increase profits while reducing operating cost, as well as meeting
government and regulatory pressures for processes to be environmentally friendly and
sustainable. Current applications of biocatalysts, more specifically, enzymes for large scale
bulk production of chemicals have been successfully applied to the production of high
fructose corn syrup, upgrading of fats and oils and biodiesel production to name a few.
Despite these examples of industrial enzymatic applications, it is still not “clear cut” how to
implement biocatalyst in industry and how best to optimize the processes. This is because
the processing strategy is usually different to most traditional catalytic processes. In nature,
enzymes operate at much lower substrate and product concentrations compared to most
industrial chemical processes. What this means is that the natural conditions for biocatalysts
are normally much different from conventional process-relevant conditions. Also, the
optimal process conditions can vary greatly from one biocatalyst to the next. Hence, to
maximize product yields and reactor productivity then the type of reactor operation and
downstream processing need to be able to address the aforementioned issues. One way to
achieve this is through process modelling to help focus the experimental work needed for
process understanding and to support further process development and optimization of the
process.
To address how the reactors should be operated; a strategy using mechanistic modelling
by combining the biological aspects of the enzyme with reaction/reactor engineering is
performed. This strategy is applied to a case study of biodiesel production catalysed by a
liquid enzyme formulation. The use of enzymes for biodiesel production is still in its infancy
with non-optimized process designs. Furthermore is it unclear how the process should be
operated to ensure optimal economics given the relatively high cost of the enzyme and the
low value of the products.