Exploring community evolutionary characteristics of microbial populations with supplementation of Camellia green tea extracts in microbial fuel cells

Abstract

This first-attempt study deciphered combined characteristics of species evolution and bioelectricity generation of microbial community in microbial fuel cells (MFCs) supplemented with Camellia green tea (GT) extracts for biomass energy extraction. Prior studies indicated that polyphenols-rich extracts as effective redox mediators (RMs) could exhibit significant electrochemical activities to enhance power generation in MFCs. However, the supplementation of Camellia GT extract obtained at room temperature with significant redox capabilities into MFCs unexpectedly exhibited obvious inhibitory effect towards power generation. This systematic study indicated that the presence of antimicrobial components (especially catechins) in GT extract might significantly alter the distribution of microbial community, in particular a decrease of microbial diversity and evenness. For practical applications to different microbial systems, pre-screening criteria of selecting biocompatible RMs should not only consider their promising redox capabilities (abiotic), but also possible inhibitory potency (biotic) to receptor microbes. Although Camellia tea extract was well-characterized as GRAS energy drink, some contents (e.g., catechins) may still express inhibition towards organisms and further assessment upon biotoxicity may be inevitably required for practice.

Keywords: Bioelectricity generation; Camellia green tea; Community ecology; Microbial fuel cells (MFCS).

Fig. 1

HPLC analysis of (A) GA (B) EGCG (C) CAF compared with tea extract and (D) HPLC analysis of tea extracts between water extract and MEOH extract . (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Peak retention time of standard (A) GA (B) EGCG and (D) CAF by HPLC at different concentrations and (D) the summary diagram of calibration curve.

Fig. 3

Comparison CV profiles of (A) water extract and (B) MEOH extract of green tea at different scan cycle . (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

The chemical structure and comparison CV profiles at different scan cycle of standard (A) GA and (B) EGCG.

Fig. 5

Power density profiles of (A) MFC-A1 and (C) MFC-B1 supplemented with water extract and (B) MFC-A2 and (D) MFC-B2 supplemented with MEOH extract.

Fig. 6

Classification of the 16S rRNA gene sequences of clone library from (A) MFC-A and (B) MFC-B: Phylum, Class, Order and Family level category of total bacteria (from left to right).