An innovative and sustainable process for producing poly(3-hydroxybutyrate-co-3-hydroxyvalerate): simulating volatile fatty acid role and biodegradability
Claudia Amabile, Teresa Abate, Carmen De Crescenzo, Raúl Muñoz, Simeone Chianese, Dino Musmarra
Abstract
Renewable resources, such as biogas and volatile fatty acids from organic substrate digestion, are used to generate the poly(3-hydroxybutyrate-co-3-hydroxyvalerate), a biopolymer with mechanical and thermal characteristics comparable with fossil fuel-based plastic. A double-stage fermentation was simulated for generating poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and analysing the role of odd fatty carbon acids on 3-hydroxyvalerate building block inclusion. Valeric acid was then supplied at various concentrations of 100–2000 ppm since it was responsible for the highest 3-HV molar fraction accumulated. The recovery of granules of biopolymer through non-halogenated extraction was also simulated: methyl ethyl ketone was employed for solubilising the granules, and a mixture of methanol and water (7:3) was applied during the precipitation stage. The recovery yields ranged from 78% to 96%, basing on the amount of polymer entering the extraction line, i.e. 0.5 and 2.5 kg, with a 3-hydroxyvalerate content of 40%mol and 20%mol, respectively. The biopolymer with the lowest and highest 3-hydroxyvalerate content were finally used for the theoretical assessment of biodegradability: a maximum weight loss of 90% was obtained for the polymer containing the highest 3-hydroxyvalerate fraction, thus confirming the dependence of the biodegradability on the biopolymer molecular structure.