Automated nutrient screening system enables high-throughput optimisation of microalgae production conditions

Radzun, Khairul Adzfa; Wolf, Juliane; Jakob, Gisela; Zhang, Eugene; Stephens, Evan; Ross, Ian L.; Hankamer, Ben

doi:10.1186/s13068-015-0238-7

Cited by 62 publications

(68 citation statements)

References 37 publications

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“…However, this increase in yield needs to be coupled with improvements in phototrophic algal biomass production in order to make the platform commercially competitive. Such improvements will come from a combination of media optimization [66], improvements in photobioreactor (PBR) design [67] and strain domestication, such as selection for reduced light-antenna mutants that show higher productivity in PBRs as a consequence of greater light penetration [68]. Alternatively, it might be more cost-effective to switch to mixotrophic production in PBRs, or heterotrophic cultivation in fermenters, where much higher biomass productivity can be achieved [69].…”

Section: Summary and Perspectivesmentioning

confidence: 99%

The algal chloroplast as a synthetic biology platform for production of therapeutic proteins

2018

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The chloroplast of Chlamydomonas reinhardtii and other microalgae represents an attractive new platform for the synthesis of recombinant therapeutics using synthetic biology (synbio) approaches. Transgenes can be designed in silico, assembled from validated DNA parts and inserted at precise and predetermined locations within the chloroplast genome to give stable synthesis of a desired recombinant protein. Numerous recent examples of different therapeutic proteins produced successfully in the C. reinhardtii chloroplast highlight the potential of this green alga as a simple, low-cost and benign host. Furthermore, some of the features of the alga may offer additional advantages over more-established microbial, mammalian or plant-based systems. These include efficient folding and accumulation of the product in the chloroplast; a lack of contaminating toxins or infectious agents; reduced downstream processing requirements; the possibility to make complex therapeutics such as immunotoxins; and the opportunity to use the whole alga as a low-cost oral vaccine. In this paper we review the current status of algal chloroplast engineering with respect to therapeutic proteins. We also consider future advances in synbio tools, together with improvements to recipient strains, which will allow the design of bespoke strains with high levels of productivity.

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Section: Summary and Perspectivesmentioning

confidence: 99%

The algal chloroplast as a synthetic biology platform for production of therapeutic proteins

2018

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“…The initial photoheterotrophic microwell plate trials allowed the refinement of screening methodology in developing the nutrient screens, which was later developed into a fully robotic system (Radzun et al, 2014). A number of commercially available strains were assayed using four different nitrogen compounds, four different carbon sources and four minor nutrients.…”

Section: Discussionmentioning

confidence: 99%

“…By combining these results, an optimal media that addresses the nutritional requirements for improved growth rate can be formulated. These results formed the foundations for the photoautotrophic nutrient screens (Radzun et al, 2014). By utilising photoheterotrophic modes of growth in the early stages of development, the culture growth cycles were shortened due to lack of automation and the absence of a CO2 controlled atmosphere.…”

Section: Nitrogen and Glycerol Nutrient Screensmentioning

confidence: 99%

Enhanced microalgae growth and lipid production: a study of cytostatic inhibitors and glycerol assimilation

Zhang¹

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Current microalgal cultivation strategies and the unrefined oil produced (priced at ~USD$294/barrel) (Benemann et al, 2012), have yet to produce globally significant amounts of commercially viable biofuels competitive with fossil derived crude oil currently at (USD$45.22/barrel WTI (Nymex) as of 28.08.2015) (Nasdaq, 2015). Underlying this issue is the economics of gross lipid production, a function of lipid content and cellular productivity. The survival response of microalgal strains that promote the accumulation of carbon as lipids typically occurs under stress conditions (such as nutrient deficiency) at the expense of cellular growth. This study explored alternative strategies that inhibit metabolic processes, cell growth and division, through the use of cytostatic inhibitors such as sodium oxamate and conazole fungicides to induce lipid production in the absence of low nutrient conditions. Additionally, the exogenous supply of glycerol as a potential source of additional carbon was also investigated to improve photoautotrophic microalgae growth.An inducible trigger for the rerouting of carbon towards lipid synthesis under nutrient replete conditions has great potential for research and commercial applications of microalgal biofuels.Photoautotrophic growth of locally collected strains was optimised through nutrient screens and subsequently dosed using the tested inhibitors. The testing of these inhibitors showed that sodium oxamate was able to inhibit cell division and increase the lipid content in most of the tested microalgae strains. On the other hand, conazole treatment was largely observed to decrease the cellular biomass of the microalgae, which suggests that carbon assimilation may have been reduced.The results indicate that both types of inhibitors were able to cytostatically affect most of the tested strains and that a number of strains responded well with increased lipid production. This process has allowed us to test the effectiveness of the compounds and to identify potential high lipid producers. Some species of microalgae are able to supplement CO2 fixation with the utilisation of exogenous carbon substrates, typically acetate or glucose. By exploring their facultative heterotrophic capabilities, photoautotrophic limitations such as light shading may be overcome. From a biotechnological perspective it would be advantageous if waste carbon streams from other processes could be used to supplement microalgal growth. One such byproduct is glycerol from the biodiesel industry. The radiolabelled results validated that glycerol is assimilated into central metabolism of Chlorella protothecoides and may be able to contribute towards cellular growth.The data presented in this thesis highlights that the microalgal metabolic diversity for particular biotechnological applications can be probed and manipulated by utilising inhibitors and substrates known to function on specific metabolic pathways. In chapter two, the hypothesis that sodium 3 | P a g e oxamate can induce lipid production in microalga...

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“…reinhardtii CC125 was purchased from Chlamydomonas Resource Centre (St Paul, USA). Precultures were grown in 20 ml of photoautotrophic medium (TAP minus acetate, Harris (2001)) in 100 ml flasks with gas-permeable lids, and maintained on shakers (200 rpm) in an enclosed system (TECAN, Melbourne), as described by Radzun et al (2015). The atmosphere of the enclosed system was purged with 1.2% CO2 and 4 L.min -1 air.…”

Section: Culture Conditionsmentioning

confidence: 99%

“…The enclosed TECAN system provided three shakers designed to hold six microwell plates per shaker (18 total) and is described in Radzun et al (2015). Each plate was custom-fitted with 96 uniformly distributed warm white light-emitting diodes (LEDs) that are controlled by user-defined scripts using an Arduino® integrated circuit controller and software, allowing coding of 18 different light conditions.…”

Section: Light Simulation and Experimental Setupmentioning

confidence: 99%

Photosynthesis of microalgae in outdoor mass cultures and modelling its effects on biomass productivity for fuels, feeds and chemicals

Yarnold¹

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Practical applications of microalgae include uses as feedstocks for sustainable fuels, feeds, nutraceuticals, and chemicals; for the treatment of wastewater and industrial flue gas; and for use as recombinant protein expression systems. Improvements in biomass yields are required for commercially viable and sustainable algal technologies, particularly for low value commodities such as biofuels.Although several algae exhibit higher growth rates than terrestrial crops, with theoretical upper limits of 8-10% photon conversion efficiency (PCE), solar-illuminated outdoor microalgal production systems typically have a PCE far below this and even below those achieved under laboratory conditions. The most intractable limiting factor is poor light distribution through the mass culture, where photoinhibitory light at the surface and dark zones deeper in the culture reduce photosynthetic productivity. Moreover, microalgae have evolved a suite of photoacclimation and photoregulation mechanisms to cope with rapid (seconds to minutes) light fluxes in natural environments, yet these processes remain poorly understood in well-mixed photobioreactors.The aim of this thesis study was to combine an experimental and theoretical approach to: 1) investigate and understand the photosynthetic response of algae under mass culture conditions; 2) develop a mathematical model which could accurately predict light-tobiomass productivities under a broad range of design scenarios for outdoor production systems; and 3) identify key biological and design parameters to maximise biomass yields.In the first part of the study, a light-to-biomass model was developed that could be easily applied to rapidly assess biomass yields of different algal strains under a range of design scenarios. This model predicts temporal and spatial irradiance at the reactor surface and through the mass culture with inputs of local solar radiation data, local coordinates, system properties and the optical properties of the culture. Local growth rates are then coupled to local light intensities within the reactor based on a static Haldane growth model derived from empirical growth-irradiance curves. Growth rates are integrated over space and time to compute areal and volumetric productivities.Validation of the model was attempted by conducting batch harvest experiments in a laboratory scale photobioreactor matrix which simulated diurnal light cycles representative of three 'typical' days of solar radiation in Brisbane. The strains used were ii Chlamydomonas reinhardtii and its truncated light-harvesting antenna mutant, tla1, reported to possess improved optical properties. Initially, the model did not satisfactorily predict growth under batch cultivation for the three different incident light conditions, overestimating productivity under low light days and overestimating on high light days.Subsequent adjustment of the model to include photoacclimative changes in the optical properties of the cell and a re-fit of the growth parameter values provided a more accurate m...

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Automated nutrient screening system enables high-throughput optimisation of microalgae production conditions

Cited by 62 publications

References 37 publications

The algal chloroplast as a synthetic biology platform for production of therapeutic proteins

The algal chloroplast as a synthetic biology platform for production of therapeutic proteins

Enhanced microalgae growth and lipid production: a study of cytostatic inhibitors and glycerol assimilation

Photosynthesis of microalgae in outdoor mass cultures and modelling its effects on biomass productivity for fuels, feeds and chemicals

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