Energy-efficient algal culture through aeration-less oxygen removal in a gas-permeable bag photobioreactor

Abstract

Closed photobioreactors are ideal for the production of high-value and high-purity microalgal products. However, dissolved oxygen accumulation in closed reactors is detrimental to algal growth. A recently developed gas-permeable bag photobioreactor removes dissolved oxygen by diffusion through its reactor surface and enables energy-efficient aeration-less operation. In this study, the gas-permeable reactor was tested in continuous culture of Arthrospira platensis, and the results were used for energy estimation. The continuous culture of A. platensis reached high productivity of 2.0 g L−1 d−1, 28.9 g m−2 d−1, and 9.3 % photosynthetic efficiency under limited mixing and aeration. Although dissolved oxygen inhibition still occurred, productivity was up to 2-fold higher than that with a non-permeable bag reactor. The energy efficiency was 2 to 5 times higher than that with non-permeable reactors, and can be >98 % efficient than conventional operations with intensive mixing. This study demonstrated effective energy-efficient mass cultivation with the novel gas-permeable reactor.