Secreted Metabolite Production in Perfusion Plant Cell Cultures

Abstract

Operation of a novel bioreactor that allows continuous perfusion cultivation of plant cell suspensions is described in this paper. This external-loop, air-lift bioreactor has an internal settling zone for cell separation. The settling zone is created by inserting a baffle plate into the upper portion of the downcomer. Using this bioreactor, an Anchusa officinalis suspension culture was cultivated to a cell density of 27.2 g DW L-1 in 14 days at a perfusion rate of 0.123 day(-1). The maximum total extracellular protein concentration attained was 1.11 g L-1. Complete cell retention was achieved throughout the culture during which the maximum packed cell volume (PCV) exceeded 80%. In comparison, the maximum cell density and extracellular protein concentration in the batch culture were 12.6 g DW L-1 and 0.47 g L-1, respectively. A very high acid phosphatase activity was observed in the spent medium of both batch and perfusion cultures. After 14 days of cultivation, the acid phosphatase activity in the batch and the perfusion cultures exceeded 2000 and 4000 units L-1, respectively. The potential application of this perfusion bioreactor in culturing cyanobacteria and other photosynthetic microorganisms for hydrogen production is also discussed.