Enzymatic degradation of poly([R,S] ?-hydroxybutyrate)

Enzymatic degradability of isotactic versus syndiotactic poly(β‐hydroxybutyrate)

“…Decreasing crystallinity increases degradability 16-I*), but synthetic racemic material 17, 26) or synthetic stereocopolymers with greater than 80% total R content *") are less degradable than natural PHB with greater crystallinity, due to the presence of undegradable S units. However, where either total S content2") or distribution of S units '7,26) is such that crystallinity is severely disrupted, the degradability of the synthetic polymer is greatly increased.…”

Degradable polymers for the future

“…In contrast to the isotactic bacterial copolyesters that have a random stereosequence, the synthetic polyesters are blocky and only partially stereoregular [51-531. The [A-stereoblock halt the enzymatic degradation and thus make it difficult for the depolymerase to penetrate into the surface and access the available [R]-stereoblocks [54].…”

Ring‐opening copolymerization of racemic β‐butyrolactone with ϵ‐caprolactone and δ‐valerolactone by distannoxane derivative catalysts: study of the enzymatic degradation in aerobic media of obtained copolymers

“…It should be mentionned that the effect of the molecular weight the of samples may not be important in determining suceptibility toward biodegradation except for samples with low molecular weights. In fact, a recent study conducted on two samples of bacterial PHB having number‐average molecular weights of 780 000 and 22 000 g mol −1 and comparable crystallinity showed essentially the same rate constant toward enzymatic degradation 12. 19 For a sufficiently low molecular weight sample, the higher solubility in the reaction medium and hence the greater surface exposure to the enzyme active sites, should result in a higher degradation rate compared with a similar sample of high molecular weight.…”

“…Marchessault et al 11, 12 prepared PHB polymers by polymerization of racemic β‐butyrolactone ( R,S )‐β‐BL in the presence of AlMe 3 /H 2 O catalyst and separated them into isotactic, atactic and syndiotactic fractions. The fraction with high isotactic diad tacticity content showed little or no degradation over a 60‐h incubation period, whereas the fraction of intermediate isotactic diad content degraded in a continous, steady way at a rate that was less than that for bacterial PHB.…”