An Automated Induction Microfluidics System for Synthetic Biology

The expression of a recombinant gene
in a host organism through
induction can be an extensively manual and labor-intensive procedure.
Several methods have been developed to simplify the protocol, but
none has fully replaced the traditional IPTG-based induction. To simplify
this process, we describe the development of an autoinduction platform
based on digital microfluidics. This system consists of a 600 nm LED
and a light sensor to enable the real-time monitoring of  the
optical density (OD) samples coordinated with the semicontinuous mixing
of a bacterial culture. A hand-held device was designed as a microbioreactor
to culture cells and to measure the OD of the bacterial culture. In
addition, it serves as a platform for the analysis of regulated protein
expression in E. coli without the requirement
of standardized well-plates or pipetting-based platforms. Here, we
report for the first time, a system that offers great convenience
without the user to physically monitor the culture or to manually
add inducer at specific times. We characterized our system by looking
at several parameters (electrode designs, gap height, and growth rates)
required for an autoinducible system. As a first step, we carried
out an automated induction optimization assay using a RFP reporter
gene to identify conditions suitable for our system. Next, we used
our system to identify active thermophilic β-glucosidase enzymes
that may be suitable candidates for biomass hydrolysis. Overall, we
believe that this platform may be useful for synthetic biology applications
that require regulating and analyzing expression of heterologous genes
for strain optimization.