Biodegradable polymers production from volatile fatty acids

Transcription

1 Biodegradable polymers production from volatile fatty acids Luísa S. Serafim, Paulo. Lemos, Maria G.E. Albuquerque, Marta Eiroa, Ana M. Ramos, Maria A.M. Reis 1 -Dep. de Química, QFB/REQUIMTE, FT/UNL, aparica, Portugal. 2 - Instituto de Tecnologia Química e Biológica (ITQB), UNL, Oeiras, Portugal 1

2 Outline Overview PHA production from VFAs Polymer characterization Microbiology 2

3 The beginning problem identification Synthetic plastics Biodegradable plastics millions of tons/year world production <20% recycled or incinerated >80% in landfills and marine environments ~25 million tons/year of waste in Europe and US Synthetic plastics ~1 /Kg Polylactic acid /Kg Starch compounds /Kg Main disadvantage: OSTS Polyhydroxyalkanoates /Kg 3

4 PHA characteristics and applications linear polyesters; thermoplastics; 100% resistance to water; molecular weight : 2 x x 10 6 ; biodegradable; biocompatible; commercial brands: Biopol P(HB/HV), Nodax P(HB/HHx), Biomer PHB, Biocycle PHB e P(HB/HV); Two types of PHA: scl-pha if R= H, H 3, 2 H 5, 3 H 7 Mcl-PHA if R= (H 2 ) 3 H 3 to (H 2 ) 8 H 3 O H O (H 2 ) n R R = H 3 PHB poly-3-hydroxybutyrate R= 2 H 5 PHV poly-3-hydroxyvalerate scl-pha bear similar characteristics to polypropylene and, according with Noda et al. (2005), mcl-pha are similar to low density polyethylene 4

5 PHA - costs Three main factors responsible for the high costs: Organisms: pure cultures and genetically modified microorganisms with the additional step of sterilization; arbon substrate: expensive carbon sources like sugars; Extraction step 5 Possible solutions: Mixed cultures Raw substrates

6 PHA - applications 6

7 PHB synthesised by activated sludge occurs under conditions without growth limitation; in biological wastewater treatment processes, microorganisms usually grow under transient conditions; storage as a response to the transient conditions. enhanced biological phosphate removal, EBPR; transient carbon supply (feast and famine); microaerophilic-aerophilic process (O 2 limitation); 7

8 Aerobic dynamic feeding: ADF Acetate, PHB (g/l); µ (h -1 ) Famine Feast arbon source PHA ell growth Famine 0 Time after pulse (h) Long period of starvation Excess of external carbon substrate Stored PHA as energy and carbon source Internal limitation Physiological adaptation ompetitive advantage 8 Simultaneous growth and PHA storage

9 ADF: Operating conditions Feeding pump Operating conditions ph: not controlled temperature: 22º po2: 100% HRT: 1 day cell RT: 10 days Biomass: 2-3 g/l 30 mmol/l 1.4 N mmol/l Withdrawing pump Aerobiosis 10.0h 9 Feeding 0.25h Settling 1.0h Withdrawing 0.5h

10 ADF: acetate as carbon source 40 Feast Famine 1.4 HAc (mmol/l); HB (mmol/l); OUR (10mmol/mmol.h) (NH 4 Nmmol/l) Time (h) HAc PHB Ammonia OUR Serafim et al. (2004) Biotechnology and Bioengineering, 87(2), Dias et al. (2005) Biotechnology and Bioengineering (in press)

11 ADF: propionate as carbon source HProp (mmol/l) HB, HV (mmol/l); NH 4(Nmmol/l); OUR (100mmol/mmol X.h) Time (h) 11 Lemos et al. (accepted) Journal of Biotechnology HProp HB HV Ammonia OUR

12 Other VFAs as carbon source SBR HAc HAc+HProp HProp HBut HVal HAc PHB P(HB/HV/HMV) (54:32:14) P(HB/HV/HMV) (31:47:22) PHB P(HB/HV/HMV) (32:52:16) HProp P(HB/HV) (68:32) P(HB/HV) (39:61) P(HB/HV) (28:72) - - OH H H 3 H2 O O - 3-hydroxybutyrate OH H H 2 H2 O O - H 3 3-hydroxyvalerate H 2 OH H H O H 3 H 3 3-hydroxy-2-methylvalerate O - 12 Lemos et al. (accepted) Journal of Biotechnology

13 Metabolism of PHA production Acetate Propionate HMV Butyrate Acetyl-oA O 2 Propionyl-oA 2x Hydroxymethylvaleryl-oA 2x 1x 1x Hydroxybutyryl-oA Hydroxyvaleryl-oA Valerate HB HV 13

14 ADF: butyrate and valerate as carbon sources Butyrate Valerate Butyrate, HB (mmol/l) Time (h) OURx10 2 (mmol/mmol.h); NH4 (Nmmol/l) Valerate, HB, HV, HMV (mmol/l) Time (h) OURx10 2 (mmol/mmol.h); NH4 (Nmmol/l) 14 Butyrate HB OUR Ammonia Lemos et al. (accepted) Journal of Biotechnology Valerate HB HV HMV OUR Ammonia

15 onclusions apacity of microorganisms in storing intracellular reserves is a competitive advantage in systems with dynamic feeding or nutrient limitation. The cultures adapted to a specific substrate, acetate or propionate, produced diverse polymeric compositions from the same substrate. Sugar cane molasses can be used as a source of VFAs for PHA production. Tailored synthesis of PHA is possible by using different VFA. 15 The thermal and morphological characteristics of the polymers obtained were similar to those of the commercial available (PHB and P(HB/HV))

16 Acknowledgments aterina Levantesi, Dra. Simona Rossetti, Dr. Valter Tandoi, IRSA, Rome for microbiological studies; arla Rodrigues for polymer termoanalysis; FT/MES, financial support. 16