| Grant number: | 12/51533-6 |
| Support Opportunities: | Program for Research on Bioenergy (BIOEN) - Regular Program Grants |
| Start date: | July 01, 2013 |
| End date: | June 30, 2015 |
| Field of knowledge: | Biological Sciences - Microbiology - Applied Microbiology |
| Agreement: | BE-BASIC Consortium |
| Principal Investigator: | Luiziana Ferreira da Silva |
| Grantee: | Luiziana Ferreira da Silva |
| Principal researcher abroad: | Kirsten Steinbusch |
| Institution abroad: | Waste2Chemicals (W2C) , Netherlands |
| Host Institution: | Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil |
| City of the host institution: | São Paulo |
Abstract
Recent papers and patents have shown that P(HB-co-HHx) is a promising biodegradable copolymer of the polyhydroxyalkanoate family (PHA), combining the short-chain (SC) monomer hydroxybutyrate (HB) and the medium-chain (MC) monomer hydroxyhexanoate (HHx), improving properties and applications, when compared with PHA with only SC or MC monomers. Since it can be processed into films, it is interesting to reduce its cost of production to make it a commodity. Aeromonas spp naturally produces a copolymer with 5-25 mol% HHx units, however only 10-20% of cell dry weight (CDW) is accumulated as PHA. B. sacchari accumulates up to 80% of CDW as PHB, but incorporates up to 2mol% HHx. Different strategies will be applied to produce P(HB-co-HHx) with variable HHx or MC monomer: construction of recombinants, metabolic flux and elementary mode analysis. HB fractions are obtained feeding bacteria with a sugar or sugarcane bagasse derivatives, however HHx incorporation depends on feeding with more scarce and expensive medium-chain fatty acid (MCFA). Raw material can represent up to 40% of costs of PHA production thus, finding cheaper and more sustainable alternatives is of high interest. It was found that MCFA could efficiently be produced with a mixed microbial fermentation (MMF) technology by anaerobic digestion, with the potential to transform acidified organic waste streams (acetic acid, ethanol etc.) into MCFA mixtures with a hexanoic acid yield of 0.85 mol C/mol C substrate in synthetic medium. MMF will be adapted to and optimized for a real feedstock (sugarcane bagasse and vinasse) to generate MCFA-containing streams appropriate to feed bacterial PHA production. This involves setting required effluent standards of MMF for the type and concentration of the fatty acids, or for other disturbing components (N or water content). Operation conditions and appropriate organic waste stream will be selected based on the requirements to feed PHA production. Starting from a single bacterial species, tailor-made copolymer will be produced, controlling monomer composition (MC monomer content from 0.5 to 25 mol% or more) from biomass, an approach not yet developed. Therefore the aim of this proposal is not merely incremental, having also the relevance of combining and improving two biological processes (MMF and PHA production) to contribute to sustainably produce an environmentally friendly material. (AU)
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