Abstract
Synechococcus sp. strain PCC 7942-SPc was grown at 303K in BG-11 under aeration with 60 mL/L CO2 in air. Cultures were performed either in (1) rectangular bubble column bioreactor, in (2) cylindrical test tube or in (3) air-lift bioreactor. Bioreactors were illuminated from one side by fluorescent lamps at the photosynthetic photon flux density (PPFD) of 63.2 µmol·m·-2·s -1. Single-nozzle sparger was used for the aeration.
Wall growth was observed in rectangular bubble column bioreactor. When single-nozzle was positioned at near the bottom of the test tube, wall growth was not observed. In air-lift bioreactors, wall growth was active at the bottom of downcomers. From these observations, it would appear that local liquid velocity in bioreactors has the key role in the occurrence of wall growth. The effects of aeration rate, hole size of sparger, etc. on wall growth were investigated. Aeration rates greatly increased the maximum of the ratio of ODW/OD (wall growth cell to cell in fluid). However, sparger hole size (depending on glass particle size δ) had little effect on this ratio, and did not affect overall cell wall growth.
