Mixotrophic operation of photo-bioelectrocatalytic fuel cell under anoxygenic microenvironment enhances the light dependent bioelectrogenic activity Rashmi Chandra, G. Venkata Subhash, S. Venkata Mohan ⇑ Bioengineering and Environmental Centre (BEEC), CSIR-Indian Institute of Chemical Technology, Hyderabad 500 607, India article info Article history: Received 23 October 2011 Received in revised form 23 December 2011 Accepted 26 December 2011 Available online 2 January 2012 Keywords: Photo-biological fuel cell (PhFC) Photosynthesis Microbial fuel cell Bacteriochlorophyll Wastewater treatment abstract Electrogenic activity of photo-bioelectrocatalytic /photo-biological fuel cell (PhFC) was evaluated in a mixotrophic mode under anoxygenic microenvironment using photosynthetic consortia as biocatalyst. An acetate rich wastewater was used as anolyte for harnessing energy along with additional treatment. Mixotrophic operation facilitated good electrogenic activity and wastewater treatment associated with biomass growth. PhFC operation documented feasible microenvironment for the growth of photosyn- thetic bacteria compared to algae which was supported by pigment (total chlorophyll and bacteriochlo- rophyll) and diversity analysis. Pigment data also illustrated the association between bacterial and algal species. The synergistic interaction between anoxygenic and oxygenic photosynthesis was found to be suitable for PhFC operation. Light dependent deposition of electrons at electrode was relatively higher compared to dark dependent electron deposition under anoxygenic condition. PhFC documented for good volatile fatty acids removal by utilizing them as electron donor. Bioelectrochemical behavior of PhFC was evaluated by voltammetric and chronoamperometry analysis. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Life on earth ultimately depends on the energy derived from sun. Photosynthesis is the only process of biological importance that can harvest light energy (Taiz and Zeiger, 2010). In fact, a large fraction of the planet’s energy resources (fossil fuels) results from photosynthetic activity. During the last decade, escalating use of fossil fuels associated with CO 2 emissions, and related environ- mental issues initiated the search for alternative technologies which generate energy from renewable resources (Tilche and Galatola, 2008). With increasing concern about sustainable energy supplies and waste minimization, solar energy gained much atten- tion to tap enormous resource for powering future generations. Photo-bioelectrocatalytic/photo-biological fuel cell (PhFC) is one such application where the photosynthetic organisms act as bio- catalyst to transform light energy to bioelectricity by utilizing CO 2 or organic sources as substrates. Microbial fuel cell (MFC) has gained a great deal of attention in recent years for its capacity to convert organics to bioelectricity through dark-fermentation (Venkata Mohan et al., 2007, 2008a; Chae et al., 2009; You et al., 2008). Unlike dark-fermentative condition, very few and specific reports are available on the usage of photosynthetic mechanism for fuel cell operation. Most of these studies relates to single strains of green algae, cyanobacteria and photosynthetic bacteria acting as anodic biocatalyst by adopting either photoautotrophic or photo- heterotrophic mode of nutrition. The metabolic activity of the bio- catalyst used and nutrition mode adopted generally governs the efficiency of PhFC. Photoautotrophic mode integrated with oxy- genic photosynthesis condition was studied with Chlamydomonas reinhardtii, Phormidium, Nostoc, Spirulina, Anabaena, Synechocystis PCC-6803, etc. as anodic biocatalyst (Venkata Mohan et al., 2008d; Pisciotta et al., 2010; Rosenbaum et al., 2005; Zou et al., 2009). Photoheterotrophic mode of nutrition was mostly evaluated with anoxygenic photosynthesis condition using photosynthetic bacteria like Rhodopseudomonas palustris, Rhodobacter sphaeroides, Rhodobacter, Rhodopseudomonas, etc. as biocatalyst (Xing et al., 2008; Cho et al., 2008; Rosenbaum et al., 2005; Scheuring et al., 2006; Yeliseev et al., 1996). Photoautotrophic mode of PhFC oper- ation reported to yield lower power output compared to the pho- toheterotrophic mode of operation. The oxygenic photosynthetic microenvironment prevailing under photoautotrophic condition neutralizes the electron prior to reaching the electrode which re- sult in lower power output. The aim of this study is to explore the potential of mixotrophic operation, on photo-bioelectrocatalytic/PhFC operation using pho- tosynthetic consortia as biocatalyst. The possibility of light depen- dent electrogenic activity (i.e., capability of depositing electrons to the extracellular environment in response to illumination) will be evaluated in mixotrophic operation, by harvesting light energy through utilization of organic carbon from wastewater and CO 2 in a PhFC operated with an open-air cathode and non-catalyzed 0960-8524/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2011.12.135 ⇑ Corresponding author. Tel.: +91 40 27191664. E-mail address: vmohan_s@yahoo.com (S. Venkata Mohan). Bioresource Technology 109 (2012) 46–56 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech