Effects of fermentation residues on the melt processability and thermomechanical degradation of PHBV produced from cheese whey using mixed microbial cultures

Two polyhydroxy(butyrate-co-valerate) (PHBV) produced from mixed microbial cultures (MMC) fed with fermented cheese whey (CW) and recovered with different down streaming routes, were processed into filaments by plasticating extrusion. The thermorheological characteristics were improved when fermentation residues were recovered together with the MMC PHBV polymer. Thermogravimetric analysis of the extruded filaments showed that MMC PHBV with 11% residues was less degraded than pure PHBV after the thermomechanical processing. Infrared spectroscopy indicated that residues rich in OH groups were volatilized during extrusion, thereby originating filaments that were less degraded than those produced with purified MMC PHBV. Residues had no impact on the semi crystalline properties of the filaments, but were responsible for their depressed mechanical properties, significant color deterioration upon processing and narrowed the processing operating window of MMC PHBV.