Microalgae as future bioresources for biofuels and chemical production

Transcription

1 Microalgae as future bioresources for biofuels and chemical production Jo Shu Chang Department of Chemical Engineering Center for Bioscience and Biotechnology Research Center for Energy Technology and Strategy Energy/Environmental Biotechnology & Biochemical Engineering (E/EBBE) Lab Website: Evolution of feedstock for biofuels First generation biofuels Oil-rich plants Second generation biofuels Third generation biofuels

2 Biofuel development at E/EBBE NCKU Energy/Environmental Biotechnology & Biochemical Engineering (E/EBBE) Lab Agricultural waste (1st/2nd generation biofuels) Saccharification Pretreatment Ethanol Butanol Transesterification Biodiesel (3rd generation biofuels) Microalgae Fermentation Hydrogen Methane Anaerobic digestion Photosynthesis mechanism CO 2 fixation irradiation Glucose Carbohydrate production 2

3 Microalgae convert starch/sugar into lipid when under stress Lipid production Microalgae as the new generation of feedstock for biofuels and chemical production Microalgal lipids Biodiesel or green diesel (TAG with 16C-18C fatty acids) Jet fuel (TAG with C fatty acids) Health food (DHA & EPA - highly unsaturated fatty acids, HUFA) Microalgal carbohydrates Bioethanol, biobutanol, etc. Carbon source for any kind of fermentative chemicals production Oligosaccharide Microalgal proteins Animal feed Fish feed Amino acids and peptides production Nitrogen source for fermentation 3

4 Integrated microalgae technology CO 2 capture & microalgae cultivation Strain improvement Photo- bioreactor Product extraction Applications Lipid-rich Microalgae Chemical or physical treatment Lipid/oil Fatty acid Biodiesel CO 2 CO 2 fixation from flue gas Mutation Harvest & Separation Reducing sugar Biomass residue Protein Bioethanol Animal feed Genetic engineering Pigment Health food 4

5 Photobioreactor for microalgal CO 2 fixation 5

6 Optimizing CO 2 feeding Effect of CO 2 flow rate and CO 2 concentration on CO 2 fixation ability CO 2 consumption rate ~ mg L -1 d -1 Enhancing photosynthesis Effect of light intensity and Mg 2+ concentration on CO 2 fixation ability CO 2 consumption rate>800 mg L -1 d -1 CO 2 consumption rate (mg L -1 d -1 ) Light intensity (u mol m -2 s -1 ) Mg 2+ concentration (m M) Best condition: CO 2 2.5% 0.4vvm Best condition: mol m -2 s -1 ; 2.2 mm Mg Photobiorector approach Fed-batch cultivation of S. obliquus CNW-N N to improve CO 2 biofixation Biomass concentration (g L -1 ) % replacement 12.5%, 25% and 50% replacements Repeated 5 times in PBR Time (d) Biomass concentration (g L -1 ) % replacement Biomass concentration (g L -1 ) % replacement Time (d) Time (d) 6

7 Performance of fed batch cultivation for CO 2 fixation CO 2 fixation in terms of bicarbonates using cyanobacteria Microalgae strains Nanochlorum sp. HT-1 CO 2 absorption Medium with HCO 3 - or CO 3 2- Photobioreactor Flue gas Thermosynechococcus sp. CL-1 (TCL-1) Collaborate with Prof. Chu (NCKU) Fast CO 2 biofixation and microalgae growth ( max > 2-3 d -1 ) Thermophilic (> 70 o C) and high alkali (ph > 8.5) conditions 7

8 The other source of CO 2 for microalgae - Any type of fermentation process will do BioH 2 fermentation (40-60% CO 2, other gas: H 2 ) Ethanol fermentation (nearly 100% CO 2 ) Butanol fermentation (~70% CO 2, some H 2 ) 8

9 Microalgae can produce much more oil than any other oil based energy crops Feedstock Gallons Oil /Acre/Year Corn 15 Soybeans 48 Safflower 83 Sunflower 102 Rapeseed 127 Micro Algae Micro Algae 1850 [based on actual biomass yields] [theoretical laboratory yield] Cultivating Algae for Liquid Fuel Production ( Microalga strain Chlorella vulgaris ESP-31 Nitrogen starvation Nutrient starvation CO 2 loading rate 9

10 Current strategies for microalgal oil production Microalgal strain Chlorella vulgaris ESP-31 Basal medium Photobioreactor design Tubular type 1.5 L 50 L Photobioreactor type Biomass production (g/l) Lipid content (%) Lipid productivity (g/l/d) Indoors (Flask-type) Indoors (1.5 L Tubulartype) Outdoors (50 L Tubulartype)

11 Microalgal cell wall Cytoplasm: starch Inner cell wall: cellulose Outer cell wall: pectin, alginate, agarose, etc. (valuable sugars) Cellulose is the major component of microalgal cell wall Functions: protection, maintenance The major components of cell wall in different algae 11

12 Advantages of microalgae sugars over lignocellulosic sugars The form of microalgae sugar Starch or glycogen (in cytoplasm) Cellulose (in inner cell wall) No lignin and low hemicellulose content No need to deal with pentose fermentation No need to apply harsh pretreatment Mainly hexose Suitable for producing ethanol or chemical Saving money and energy Less pollution Carbohydrates production from different feedstock 12

13 Medium: Sugar production under stress Chlorella vulgaris FSP-E Basal medium Work volume: 1 L Agitation rate: 150 rpm Cultivation condition: Photoautotrophic growth Aeration: CO 2 2%, 0.2 vvm Effect of nitrogen starvation on carbohydrate composition of Chlorella vulgaris FSP E Medium: Basal medium Cultivation condition: Photoautotrophic growth Aeration: CO 2 2%, 0.2 vvm Nitrogen concentration: 12.4mM Nitrogen sources: (NH 2 ) 2 CO Light intensity: 60 mmol m -2 s -1 Inoculation : 0.02 g/l before Cultivation time under nitrogen starvation (days) 13

14 Carbohydrate composition of Chlorella vulgaris FSP E (under autotrophic growth with 2% CO 2 & 0.2 vvm) Day Carbohydrate (%) Lipid (%) Protein (%) Others(%) ± ± ± ±0.10 Day Glucose (%) (cellulose + starch) Starch (%) Xylose + Galactose (%) Hemicellulose Arabinose (%) Rhamnose (%) ± ± ± ± ± ± ± ± ± ±0.02 Comparison of carbohydrate productivity from different microalgal strains Strains Operation mode Growth (days) Biomass production (g/l) Carbohydrate content (%) Carbohydrate productivity (g/l/d) References C. vulgaris Batch Illman et al., 2000 C. vulgaris Batch 41.0 (starch) Dragone et al., 2011 C. reinhardtii Fed-batch ( Nguyen et al., 2009 starch) C. reinhardtii Batch Kim et al., 2006 T. subcordiformis Semi-CSTR Zheng et al., 2011 Nannochloropsis sp. Batch Cheng et al., 2008 S. obliquus Batch Ho et al., 2010 C. vulgaris Batch ± This study FSP-E C. vulgaris FSP-E: Growth 5.5 days including 3-day nitrogen starvation period. 14

15 Bioethanol produced from microalgae Resource Feedstock Product Enzymatic hydrolysis Water N-source Minerals Algae powder Fermentation Advantages No lignin content (so, no pretreatment is needed) Mainly hexose (so, no pentose fermentation problems) bioethanol Strain: Chlorella vulgaris FSP-E 90% of theoretical yield Algal hydrolysate : Initial glucose conc.: (g/l) Hydrolytic enzymes (EM2) Endoglucanase: 0.65 U/m -glucosidase: 0.3 U/m Amylase: 0.75 U/ml 15

16 Dilute acid hydrolysis is very effective to obtain glucose from microalgal carbohydrates Sulfuric acid concentration: % Autoclave : 121, 20 min Concentration : 10 g/l Work volume : 10 ml Acidic hydrolysis of C. vulgaris FSP-E biomass for ethanol production by SHF process Microalgal biomass conc.: 60 (g/l) Glucose content: 43.5±0.3% Sulfuric acid concentration: 1.0% Condition : 121, 20 min Algal hydrolyate Initial glucose conc.: 23.6 (g/l) Ethanol fermentation SHF: Separate hydrolysis and fermentation Sugars concentration (g/l) Yield (mol ethanol/mol glucose ) Medium Acetate buffer Microalgae Medium (ethanol conc.) Acetate buffer (ethanol conc.) Microalgae (ethanol conc.) Medium (glucose conc.) Acetate buffer (glucose conc.) Microalgae (glucose conc.) Time (hr) Ethanol concentration (g/l) 87.6% of theoretical yield 16

17 Biomass productivity and ethanol yield from different feedstock Pigments production and other applications of microalgae biomass 17

18 Microalgae pigments Lutein 35 18

19 Effect of monochromatic light strategy on lutein accumulation Biomass productivity (g L -1 day -1 ) Maximal lutein content (mg g -1 ) Maximal lutein productivity (mg L -1 day -1 ) Red Blue Green Yellow Red and blue monochromatic light exhibited the best lutein productivity, where red light got highest biomass productivity and blue light maximal lutein content Phycocyanin production Spirulina sp. 19

20 Phycocyanin production from Spirulina sp. cultivated at different light intensities One-side light intensity (µmole/m 2. s) Biomass production (g/l) Protein content (%) Protein production (g/l) Protein productivity (mg/l/d) Phycocyanin content (7th day) (%) Phycocyanin content (final) (%) Phycocyanin production (mg/l) Phycocyanin productivity (mg/l/d) N.D N.D N.D N.D N.D N.D N.D N.D N.D N.D N.D N.D N.D N.D Ongoing projects and future work CO 2 re utilization process (scale up and optimization) Microalgae based biofuels (Biodiesel, bioalcohols) Biorefineryusing microalgae based carbon and nitrogen source Protein rich microalgae as aquatic feed Microalgae based cosmetic products and health food Combining microalgae cultivation with wastewater treatment Genetic engineering on microalgae (esp., eucaryotic microalgae) 20