title: Microalgal triacylglycerides production in outdoor batch-operated tubular PBRs.
abstract: BACKGROUND
  Microalgal triacylglycerides (TAGs) are a promising sustainable feedstock for the biofuel, chemical and food industry. However, industrial production of microalgal products for commodity markets is not yet economically viable, largely because of low microalgal productivity. The latter is strictly dependent on initial-biomass-specific (IBS) light availability (i.e. ratio of light impinging on reactor ground area divided by initial biomass concentration per ground area). This study investigates the effect of IBS-light availability on batch TAG production for Nannochloropsis sp. cultivated in two outdoor tubular reactors (i.e. vertical and horizontal) at different initial biomass concentrations for the TAG accumulation phase, during two distinct seasons (i.e. high and low light conditions).
  
  
  RESULTS
  Increasing IBS-light availability led to both a higher IBS-TAG production rate and TAG content at the end of the batch, whereas biomass yield on light decreased. As a result, an optimum IBS-light availability was determined for the TAG productivity obtained at the end of the batch and several guidelines could be established. The vertical reactor (VR) should be operated at an initial biomass concentration of 1.5 g L(-1) to achieve high TAG productivities (1.9 and 3.2 g m(-2) day(-1) under low and high light, respectively). Instead, the horizontal reactor (HR) should be operated at 2.5 g L(-1) under high light (2.6 g m(-2) day(-1)), and at 1.5 g L(-1) under low light (1.4 g m(-2) day(-1)).
  
  
  CONCLUSIONS
  From this study, the great importance of IBS-light availability on TAG production can be deduced. Although maintaining high light availabilities in the reactor is key to reach high TAG contents at the end of the batch, considerable losses in TAG productivity were observed for the two reactors regardless of light condition, when not operated at optimal initial biomass concentrations (15-40% for VR and 30-60% for HR).
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, The Netherlands.
authors.forename: Giulia
authors.identifier: 0000-0003-2206-5780
authors.initials: G
authors.lastname: Benvenuti
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, The Netherlands.
authors.forename: Rouke
authors.initials: R
authors.lastname: Bosma
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, The Netherlands.
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Klok
authors.affiliation: Biomass Engineering Center, China Agricultural University, P.O. Box 50, Beijing, 100083 China.
authors.forename: Fang
authors.initials: F
authors.lastname: Ji
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, The Netherlands.
authors.forename: Packo P
authors.initials: PP
authors.lastname: Lamers
authors.affiliation: Food and Biobased Research, AlgaePARC, Wageningen UR, P.O. Box 16, 6700 AA Wageningen, The Netherlands.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Barbosa
authors.affiliation: Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, The Netherlands ; Biosciences and Aquaculture, Nordland University, 8049 Bodø, Norway.
authors.forename: René H
authors.initials: RH
authors.lastname: Wijffels
keywords: Light availability; Microalgae; Outdoor; Pilot-scale; TAG productivity