A method to compute instantaneous oxygen evolution rates in cyanobacterial cultures grown in shake flasks

Abstract

Cyanobacteria have been attracting attention for various biotechnological applications due to their ability to carry out oxygenic photosynthesis. The oxygen evolution rate (OER) of cyanobacterial cultures is a key physiological parameter, which is typically measured offline by using oxygen electrodes. In situ measurement of OER has been reported in a photobioreactor fitted with a dissolved oxygen (DO) probe. Here, we show that the OER can be estimated from online measurements of the DO levels by using sensors fitted in shake flasks, which are widely used for preliminary characterization of microbial strains. We study how the DO levels change under diurnal light regime and different growth conditions in two strains of Synechococcus elongatus, namely, PCC 7942 and PCC 11801, in shake flasks. We use the DO levels coupled with the knowledge of the overall gas-liquid mass transfer coefficient for oxygen (k L a) to compute the OER.For the growth conditions tested, the cumulative oxygen evolved in a day correlated with the increase in biomass suggesting that the calculated OER, in turn, might provide an estimate of the organism's growth rate. We believe that the method may be widely applicable for the growth characterization of organisms that perform oxygenic photosynthesis. K E Y W O R D Sabiotic factors, cyanobacteria, dissolved oxygen profile, oxygen evolution rates, PreSens technology, shake flaskThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Photosynthetic Co-production of Succinate and Ethylene in a Fast-Growing Cyanobacterium, Synechococcus elongatus PCC 11801

“…Further, the glycogen content was in general higher in late phase under LL-HC and HL-HC for both the wild type and the engineered strains (Figure 3c and Figure S5). Since the recombinant strain showed increased glycogen content similar to wild type with no change in the relative abundance of ADPG (Figure 3c and 6), knockout of genes for glycogen synthesis might divert more carbon towards the pathway of interest increasing the productivity during the later phase of growth [47]. Figure 6.…”

“…Although the biomass accumulation in the bottle was lower than in shake flasks, no significant improvement in succinate titre was observed in baffled flasks as compared to unbaffled flasks or bottles (Figure S4). Cyanobacterial cultures exhibit super-saturated levels of dissolved oxygen under photoautotrophic conditions [46,47] and this may explain the lack of effect of baffles on succinate production.…”

“…It was of interest to test the effect of nitrate on succinate productivity as 2-oxoglutarate is a key precursor for the EFE enzyme. Previous reports have shown that growth in either BG110 or 1 mM NaNO3 supplemented BG11 was highly retarded with insignificant ethylene production [25,47]. Therefore, the effect of nitrate on product formation was investigated in the recombinant and wild type strains under different nitrate (NaNO3) concentrations, viz., 0.25, 0.5 and 1 (17 mM) NaNO3.…”

Cyanobacteria and Algal-Based Biological Life Support System (BLSS) and Planetary Surface Atmospheric Revitalizing Bioreactor Brief Concept Review

“…Unlike organisms in the environment which are subject to light and dark cycles and other natural cycles, these cultures were grown under controlled conditions, including continuous illumination. The peak oxygen evolution rate observed was in the range of 0.38 to 3.5 mg/L/h, depending on the growth conditions [ 51 ]. Another study measured specific oxygen production rates in the species M. aeruginosa cultured under light–dark cycles on a solid agar plate and later in a liquid medium.…”