Plastic bag as horizontal photobioreactor on rocking platform driven by water power for culture of alkalihalophilic cyanobacterium

Abstract

Background: Mixing in traditional algae culture system consumes intensive electricity. This should be replaced by nature force to reduce energy cost and, more importantly, to realize positive energy balance of algal biofuel production. This study aims to develop a horizontal photobioreactor, in which mixing can be provided with rocking movement driven by nature force.Results: Simple boxes were used as small-scale horizontal photobioreactors on a rocking platform for culture of alkalihalophilic Euhalothece sp. ZM001. There was no CO 2 gas bubbling since 1.0 M NaHCO 3 supplied sufficient inorganic carbon in it. Effect of culture depth, rocking cycle, and light intensity to algal biomass production, pH change, and DO accumulation were investigated in this system. Biomass concentration of 2.73 g/L was achieved in culture with 2.5 cm depth, and maximum productivity of 17.06 g/m 2 /day was obtained in culture with 10 cm depth. k L a in PBR with different culture depths and rocking cycles was measured, and it was from 0.57 to 33.49 h −1, showing great variation. To test this system at large scale, a plastic bag with a surface area of 1 m 2 was placed on a rocking platform driven by water power, and it resulted in a biomass concentration of 1.88 g/L. Conclusion: These results proved feasibility of a novel photobioreactor system driven by nature force, as well as low cost of manufacturing, and easy scaling-up.

Hydrodynamic performance of floating photobioreactors driven by wave energy

“…As mixing in the floating PBRs was induced by only wave movement, there must be great differences in the fluid dynamics of PBRs at different culture depths, including mixing characteristics and flashing light effects. These difference were observed in our studies [ 47 ]. To better understand these differences, CFD will be used to simulate the hydrodynamics and mixing behavior of floating PBRs at different culture depths in the future.…”

Photobioreactors for cultivation and synthesis: Specifications, challenges, and perspectives

“…The capacity of the bags is usually around 25 L, but bags up until 50 L have been reported [20,24]. An interesting exception to this is the work by Zhu et al [75], in which they use a plastic bag horizontally on a rocking platform to reduce energy cost.…”

Metabolic Engineering of the Model Photoautotrophic Cyanobacterium Synechocystis for Ethanol Production: Optimization Strategies and Challenges

“…The most frequent types of PBRs proposed are non-sterile horizontal tubular or vertical flat panel PBRs, which have several limitations including: (a) cost, which have been estimated at €2400 m 2 for small scale, reducing in cost slightly with scale [70]. This would result in a cost [70], (d) The reactor design must be able to withstand photo-oxidation, prevent evaporative loss of product, while maintaining axenic conditions as long as possible.…”

“…The most frequent types of PBRs proposed are non-sterile horizontal tubular or vertical flat panel PBRs, which have several limitations including: (a) cost, which have been estimated at €2400 m 2 for small scale, reducing in cost slightly with scale [70]. This would result in a cost [70], (d) The reactor design must be able to withstand photo-oxidation, prevent evaporative loss of product, while maintaining axenic conditions as long as possible. Given the generally slow growth, rates of cyanobacterial species, largely because of the photoautotrophic lifestyle, need to manufacture most of their metabolites, maintain a polyploid genome because of the high sunlight and UV exposure the design of PBRs suitable for low value ethanol production from cyanobacteria is a challenge.…”

“…This may have significant cost savings in terms of CO 2 sparging, transport costs and CO 2 loss due to outgassing. Bag type culturing [70] which can be once off or be reusable can offer another potential solution. This may mitigate against some of the limitations of more traditional PBRs.…”