Microalgal Bioprocessing: Process Technologies, Modelling and Optimization MBT – Fall 2014 October 28 th , 2014 Hector De la Hoz Siegler Department of Chemical and Petroleum Engineering University of Calgary [email protected]Hector De la Hoz Siegler. PhD.
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Microalgal Bioprocessing: Process Technologies, Modelling and Optimization
MBT – Fall 2014
October 28th, 2014 Hector De la Hoz Siegler
Department of Chemical and Petroleum Engineering University of Calgary
III. Optimization of heterotrophic cultures IV. Summary
INTRODUCTION TO MICROALGAL BIOTECHNOLOGY
Part I
3
Microalgae: what are they?
• Microalgae are plant-like unicellular organisms capable of producing several end-products that can be used as, or converted into, fuels: hydrogen, ethanol, oil, starch, lignocellulose.
• The term microalgae comprises a polyphyletic group of photosynthetic eukaryotes. Microalgae have a great capacity for adapting to changing environmental conditions as well as using different substrates.
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Microalgae as efficient organisms
• Benefits: • Highly efficient microorganisms
• Nutrient flexibility
• Stress adaptability
• Produce and store high amounts of oil
• Other valuable byproducts
• Challenges • Low culture density
• Slow growth: low productivity
• High production cost
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Applications
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Microalgae
Biofuels
Fine chemicals Waste-water treatment / Remediation
Pharma- and nutraceuticals
Human and animal food
CO2 Capture
Some Commercial Applications
Species/group Product Application areas Production facilities
References
Haematococcus pluvialis / Chlorophyta
Carotenoids, astaxanthin
Health food, feed additives and pharmaceuticals
Open ponds, PBR
Del Campo et al. (2007)
Odontella aurita / Bacillariophyta
Fatty acids Pharmaceuticals, cosmetics, baby food
Open ponds Pulz and Gross (2004)
Isochrysis galbana / Chlorophyta
Fatty acids Animal nutrition Open ponds, PBR
Molina Grima et al. (1994); Pulz and Gross (2004)
Phaedactylum tricornutum / Bacillariophyta
Lipids, fatty acids
Nutrition, fuel production Open ponds, basins, PBR
Yongmanitchai and Ward (1991); Acien- Fernandez et al. (2003)
Muriellopsis sp. / Chlorophyta
Carotenoids, Lutein
Health food, food supplement, feed
Open ponds, PBR
Blanco et al. (2007); Del Campo et al. (2007)
Crypthecodinium cohnii
DHA Food additive Fermenters (heterotrophic)
Carvalho et al. (2006)
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Currently, applications of microalgal biotechnology are limited to niche (small) markets. Though high value! We expect to move into large scale markets.
Biofuels: a renewable energy source
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Energy reserves / Energy consumption
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Biofuels
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• 1st Generation: derived from food-crops, i.e. ethanol from sugar cane or corn, biodiesel from canola or soybeans.
• 2nd Generation: produced from lignocellulosic materials, i.e. ethanol from wood chips, switch grass.
• 3rd Generation: fuels from microalgae
• 4th Generation: from crops designed for fuels in combination with highly efficient microbes.
Solar radiation in Alberta Fort McMurray: 4181 MJ/m2∙y Edmonton: 4510 MJ/m2∙y Medicine Hat: 5221 MJ/m2∙y Munich (GE): 4044 MJ/m2∙y Naples (IT): 5293 MJ/m2∙y Kuala Lumpur: 5622 MJ/m2∙y Orlando (FL): 5922 MJ/m2∙y Acapulco (MX): 7261 MJ/m2∙y Phoenix (AZ): 7621 MJ/m2∙y
Solar radiation data taken from: U.S. Department of Energy - EnergyPlus Weather Data. http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data.cfm
Culturing techniques: Open Ponds
• By far, the most common production system.
• Low installation cost • Lagoons or artificial ponds • High risk of contamination • Application limited to few
species (extremophiles). • Unmixed ponds: area range from
1 - 200 Ha, depth 20-30 cm • Raceway ponds are up to 1 Ha.
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Culturing: Close Ponds and Tanks
• Simpler designs similar to open ponds, with a cover (greenhouses).
• Aim to reduce contamination risks.
• Control CO2 looses. • Tanks are usually mixed by
aeration. • Deep tanks are inefficient. Bad
light transmission. • Easy to operate, low cost.
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Culturing: Photobioreactors
Tubular Photobioreactor - Algae and Biofuels Facility, South Australian Research and Development Institute
Flat Panel photobioreactor
Arizona Center for Algal Technology and Innovation
Flexible plastic film Photobioreactor - Algenol, Florida 25
Culturing: Photobioreactors
• Better culture control • Higher productivity, and culture
density • Minimal contamination risk • Well mixed • Excellent temperature control • Oxygen control is an issue • High capital investment • Frequent cleaning required • Cooling required
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Heterotrophic Production of Algae
• Some algae species can grow using an organic carbon source.
• Conventional bioreactors can be used.
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Phototrophic vs. Heterotrophic?
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Specie Oil content (%)
Cell conc. (g/L)
Oil Prod. (mg/L d) References
Ettlia oleoabundans 36 – 42 2.9 164 Griffiths et al (2009); Li et al. (2008)
Chlorella zofingiensis 25.8 1.9 35 Liu et al. (2010)
Chlorella zofingiensis 51.1 9.6 354 Liu et al. (2010)
Nitzschia laevis 16.5 22.1 914 Wen and Chen (2003)
S. Limacinum (DHA) 17.3 37.9 656 Chi et al. (2009)
A. protothecoides 38.3 – 53.0 8.4 820 Cheng et al. (2009)
A. protothecoides 50.3 – 57.8 51.1 3320 Xiong et al. (2008)
Phot
otro
phic
He
tero
trop
hic
MODEL-BASED OPTIMIZATION OF HETEROTROPHIC ALGAL CULTURES
Part III
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Bioprocess Optimization
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Strain selection
Media formulation
Process conditions
Continuous / Real-time
Genetic modification
The Objective for Optimization
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Stress Oil storing is a metabolic response to stress, particularly nitrogen deficiency. At nitrogen deficient conditions, algal cells over-accumulate lipids.
The challenge is to maximize biomass production while keeping a high oil content. It is necessary to determine the nitrogen supplementation strategy to achieve this.
Nitrogen As nitrogen is required for protein synthesis, its deficiency negatively affects growth and cell functioning. Therefore, conditions that favored oil accumulation constraint productivity.
Understanding algal growth
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Nitrogen uptake
Lipid production
Cellular growth
An algal growth model
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Cellular growth
Nitrogen uptake
Oil production
Macroscopic balances
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Optimization: Problem formulation
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Subject to:
Simulation results
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Biomass productivity in continuous cultures
Lipid productivity in continuous cultures
Experimental results
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Biomass productivity and growth rate
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Lipid productivity and production rate
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Comparative study: growth on glucose
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Specie Lipid content (%, w/w)
Oil Productivity (g/L h)
References
E. coli (gen. modified) 25.4 0.246 Elbahoul et al (2010)
R. opacus PD630 38.4 0.171 Kurosawa et al (2010)
M. ramanniana 67.7 0.17 Hiruta et al (1997)
C. echinulata 26.9 0.07 Kosa et al (2011)
R. toruloides 67.5 0.54 Li et al. (2007)
L. starkeyi 56.0 0.04 Kosa et al. (2011)
C. curvatus 82.7 0.47 Zhang et al. (2011)
Schizochytrium sp. 30 0.096 Ganuza et al (2007)
C. vulgaris 9.7 0.12 Doucha et al. (2011)
A. protothecoides 50.3 0.14 Xiong et al. (2008)
A. protothecoides 49.4 0.43 – 0.84 De la Hoz et al (2012)
Bact
eria
M
olds
Ye
asts
M
icro
alga
e
Optimization: closing remarks
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Model-based optimization of heterotrophic microalgal cultures allowed to reach very high densities, with biomass productivity greater than 30 g/L d, and as high as 70 g/L d.
High oil content (40–60% w/w) can be sustained with a lipid productivity around 20 g/L d.
High quality monitoring and control is essential to achieve high productivities.
Better control / sensors = higher productivity.
Summary
• Algae are promising organisms: highly efficient
• Good source of oil: PUFA, biodiesel precursor
• Algae can growth on simple inexpensive media
• Several reactor types and geometry. Application will limit
reactor choice
• Several successful commercial applications currently working.