High throughput evaluation of sugar beet vinasse for industrial enzyme production

High throughput, single-use cultivation systems have become increasingly important in facilitating early-stage bioprocess development. A number of microwell bioreactor system are now available offering control of key fermentation parameters such as pH and dissolved oxygen (DO) at the level of individual wells. Here, we demonstrated the utility of such a 24-well bioreactor system for high throughput evaluation of potential renewable feedstocks within the context of an integrated biorefinery. Specifically we evaluate the use of sugar beet vinasse (the by-product of bioethanol production within a sugar beet biorefinery) as a feedstock for the production of transaminase (TAm) by Escherichia coli BL21 fermentation. The transaminase is useful for the stereoselective transformation of sugar beet pulp breakdown products into value-added chemicals and pharmaceutical intermediates.

In this work the variability of vinasse composition and options for pre-processing, i.e. dilution and adsorption, were first explored. Subsequently the effects of several fermentation parameters, including inoculum concentration and vinasse supplementation with trace elements and nitrogen-containing substrates, were investigated in the 24-well microbioreactor platform. While inoculum concentration and trace elements had little impact on fermentation performance while supplementation of vinasse with 5 g L^-1 of yeast extract enhanced the maximum biomass concentration and TAm titre by 1.7- and 3.6-fold, respectively. Overall this work demonstrates the utility of microbioreactor and the suitability of using sugar beet vinasse as a feedstock for industrial enzyme production.