Microbial photosynthesis presents a valuable opportunity to capture abundant light energy to produce renewable bioenergy and biomaterials. To understand the factors that control the productivity of photosyntheticmicroorganisms, we conducted a series of semi-continuous experiments using bench-scale photobioreactor (PBR) systems, the cyanobacterium Synechocystis PCC6803 (PCC6803), and light conditions imitating actual day-night light irradiance (LI). Our results demonstrate that using normal BG-11 medium resulted in severe phosphate (Pi) limitation for continuous operation. Mitigation of Pi-limitation, by augmenting the Pi content of BG-11, allowed higher biomass productivity; however, once Pi-limitation was alleviated, limitation by inorganic carbon (Ci) or LI occurred. Ci-limitation was detected by a low total Ci concentration (<5mgC/L) and high and fluctuating pH. Ci-limitation was relieved by delivering more CO2, which led to a stable pH in the range of 7-9 and at least 5mg/L of Ci in HCO3-. LI limitation, evidenced by an average LI <14W/m2 for PCC6803, was induced by a high biomass concentration of 1,300mg/L. Thus, this work provides quantitative tools of stoichiometry and kinetics to evaluate limitation on PBRs.

Original languageEnglish (US)
Pages (from-to)553-563
Number of pages11
JournalBiotechnology and bioengineering
Issue number4
StatePublished - Jul 1 2010


  • Inorganic carbon limitation
  • Light irradiance limitation
  • Phosphorus limitation
  • Photoautotrophic biomass production
  • Rate-limiting factors

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology


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