Microbial degradation and physico-chemical alteration of polyhydroxyalkanoates by a thermophilic Streptomyces sp.

Abstract

A thermophilic Streptomyces sp. capable of degrading various aliphatic polyesters was isolated from a landfill site. The isolate, Streptomyces sp. BCC23167, demonstrated rapid aerobic degradation of several polyesters, including polyhydroxyalkanoate copolymers, poly(ε-caprolactone) and polybutylene succinate at 50• C and neutral pH. The degrading activity was repressed by glucose and cellobiose, but tolerant to repression by other carbon substrates. Degradation of a commercial poly[(R)-3-hydroxybutyrate-co-3-hydroxyhexanoate] (PHBHx) by Streptomyces sp. BCC23167 progressed from surface to bulk as suggested by the slight decrease in polymer molecular weight. Differential scanning calorimetry analysis of PHBHx film degradation by Streptomyces sp. BCC23167 showed that relative crystallinity of the film increased slightly in the early stage of degradation, followed by a marked decrease later on. The surface morphology of degraded films was analyzed by scanning electron microscopy, which showed altered surface structure consistent with the changes in crystallinity. The isolate is thus of potential for application in composting technology for bio-plastic degradation.

Review of recent advances in the biodegradability of polyhydroxyalkanoate (PHA) bioplastics and their composites

“…Furthermore, natural fibres provide the more desirable glucose as a carbon source which can slow down biodegradation by glucose repression. It is still well documented that PHA degradation is repressed in the presence of glucose and cellobiose, 282 However, once these specific carbon sources are degraded in a relative area, the PHA availability will be maximized and its biodegradation will resume. A second misinterpretation is the idea that cellulose derivatives will biodegrade, which is not always correct.…”

The Positive Fate of Biochar Addition to Soil in the Degradation of PHBV-Silver Nanoparticle Composites

“…Phithakrotchanakoon et al 46 observed that in the degradation of poly [(R) −3-hydroxybutyrate-co-3-hydroxyhexanoate] (PHBHx) by Streptomyces sp. (BCC23167) there was an increase in relative crystallinity of the film, in the early stage of degradation (<6 days), followed by a decrease in the final period.…”

Biochemical and genetic analysis of a cutinase-type polyesterase from a thermophilic Thermobifida alba AHK119

“…Several microorganisms containing these enzymes have been isolated from different sources, especially from composts (Kleeberg et al 1998;Bellia et al 1999;Longieras et al 2004) because they contain diverse microorganisms (mesophiles and thermophiles) due to the changes in temperature experienced during the maturing process and the different composting materials used. Diverse polyester-degrading thermophilic actomonycetes have been isolated (Calabia and Tokiwa 2004;Hoang et al 2007;Phithakrotchanakoon et al 2009). The thermophiles Thermobifida fusca and T. alba have been isolated from composts and are potent degraders of polyesters such as aliphatic-co-aromatic polyesters (Kleeberg et al 1998;Hu et al 2008;Sinsereekul et al 2010).…”