A novel lab-scale tubular closed photobioreactor was developed and used for the assessment of the photosynthetic activity of an alkaliphilic microalgae mixed consortium under non-substrate limitation (i.e., bicarbonate excess), controlled irradiance, and mixing conditions. Two prominent haloalkaliphilic strains were identified as members of the consortium: Halospirulina sp. and Picochlorum sp. The photobioreactor (vol=0.5 L) consists of two interconnected U-shaped borosilicate glass tubes (internal diameter 2 cm) reaching a surface/volume ratio of 200 m 2 m −3 . This configuration specifically addressed the issue of the homogeneous light distribution among the microalgae suspended cells cultured by using fixed equidistant cool white light LEDs nearby the surface of the glass tubes. A soft homogeneous pneumatic mixing (i.e., airlift) was implemented in the culture fostering Reynolds numbers around 3000. The photosynthetic activity of the microalgae consortium was evaluated during different short-term kinetic assays by fitting the dynamics of the dissolved oxygen concentration to an oxygenic kinetic model. The photobioreactor operated in a closed loop allowed to control the produced oxygen by the extraction of the cumulated gas in the headspace. The use of this novel photobioreactor allowed the photosynthetic activity of microalgae suspended cells to be assessed, where the dissolved oxygen concentration and irradiance were the main parameters affecting the oxygenic rates under alkaline pH.
The alkaline conditions enhance the CO absorption from biogas and could optimize specialized microalgae communities in the open photobioreactor. Denaturing gradient gel electrophoresis fingerprinting and richness index comparison are useful methods for the evaluation of microalgae community shifts and photosynthetic activity performance, particularly in systems intended for CO removal from biogas where the CO assimilation potential can be related to the microbial richness.
The biodegradation of the sulfonated azo dyes, Acid Orange 7 (AO7) and Acid Red 88 (AR88), by a bacterial consortium isolated from water and soil samples obtained from sites receiving discharges from textile industries, was evaluated. For a better removal of azo dyes and their biodegradation byproducts, an aerobically operated two‐stage rectangular packed‐bed biofilm reactor (2S‐RPBR) was constructed. Because the consortium's metabolic activity is affected by oxygen, the effect of the interstitial air flow rate QGI on 2S‐RPBR's zonal values of the oxygen mass transfer coefficient kLa was estimated. In the operational conditions probed in the bioreactor, the kLa values varied from 3 to 60 h−1, which roughly correspond to volumetric oxygen transfer rates, dcL/dt, ranging from 20 to 375 mg O2 L−1h−1. Complete biodegradation of azo dyes was attained at loading rates BV,AZ up to 40 mg L−1d−1. At higher BV,AZ values (80 mg L−1 d−1), dye decolorization and biodegradation of the intermediaries 4‐amino‐naphthalenesulphonic acid (4‐ANS) and 1‐amino‐2‐naphthol (1‐A2N) was almost complete. However, a diminution in COD and TOC removal efficiencies was observed in correspondence to the 4‐aminobenzenesulfonic acid (4‐ABS) accumulation in the bioreactor. Although the oxygen transport rate improved the azo dye mineralization, the results suggest that the removal efficiency of azo dyes was affected by biofilm detachment at relatively high QGI and BV,AZ values. After 225 days of continuous operation of the 2S‐RFBR, eight bacterial strains were isolated from the biofilm attached to the porous support. The identified genera were: Arthrobacter, Variovorax, Agrococcus, Sphingomonas, Sphingopyxis, Methylobacterium, Mesorhizobium, and Microbacterium.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.