Recombinant Escherichia coli BL21-pET28a- egfp Cultivated with Nanomaterials in a Modified Microchannel for Biofilm Formation

Abstract

The application of whole cells as catalytic biofilms in microchannels has attracted increasing scientific interest. However, the excessive biomass formation and structure of biofilms in a reactor limits their use. A microchannel reactor with surface modification was used to colonize recombinant Escherichia coil BL21-pET28a-egfp rapidly and accelerated growth of biofilms in the microchannel. The segmented flow system of 'air/culture medium containing nanomaterials' was firstly used to modulate the biofilms formation of recombinant E. coil; the inhibitory effects of nanomaterials on biofilm formation were investigated. The results indicated that the segmental flow mode has a significant impact on the structure and development of biofilms. Using the channels modified by silane reagent, the culture time of biofilms (30 h) was reduced by 6 h compared to unmodified channels. With the addition of graphene sheets (10 mg/L) in Luria-Bertani (LB) medium, the graphene sheets possessed a minimum inhibition rate of 3.23% against recombinant E. coil. The biofilms cultivated by the LB medium with added graphene sheets were stably formed in 20 h; the formation time was 33.33% shorter than that by LB medium without graphene. The developed method provides an efficient and simple approach for rapid preparation of catalytic biofilms in microchannel reactors.

Keywords: biofilm; microreactor; nanomaterials; recombinant Escherichia coil; surface modification.

Figure 1

Growth of recombinant E. coli BL21-pET28a-egfp biofilms in a microchannel reactor under different flow modes.

Figure 2

Effects of different flow rates (A), pH (B), and temperature (C) on the formation of recombinant E. coli BL21-pET28a-egfp biofilms.

Figure 3

The photos of recombinant E. coli BL21-pET28a-egfp on unmodified (A) and modified (B) microchannel surfaces under inverted fluorescence microscope. The photo of recombinant E. coli biofilms on the modified microchannel surfaces under inverted fluorescence microscope after 30 h (C). The total biomass of recombinant E. coli biofilms were compared in unmodified and modified microchannels (D).

Figure 4

Effects of different nanomaterials and concentrations on growth of biofilms (A) and recombinant E. coli BL21-pET28a-egfp (B). The growth of recombinant E. coli biofilms with graphene nanomaterial was measured under segment flow mode (C). The SEM patterns of biofilms formed in microchannels with LB medium (D), LB medium containing graphene sheets (10 mg/L) (E), and graphene sheets (F).

Figure 5

The FT-IR spectra (A) and X-ray diffraction patterns (B) of biofilms formed with LB medium and LB medium containing graphene nanomaterials (10 mg/L) in a microreactor by segment flow. Biofilm formed with LB medium (a,d); biofilm formed with LB medium containing graphene nanomaterials (10 mg/L) (b,e); graphene nanomaterials (c,f).