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Poly(hydroxyalkanoates) (PHAs) are bacterial storage polyesters, currently receiving much attention because of their potential as biodegradable and renewable plastics. Well known are poly(hydroxybutyrate) and its copolymers with hydroxyvalerate, which have been commercialised under the trademark Biopol. In addition to these rigid materials, the elastomeric medium-chainlength PHAs (mcl-PHAs) from¯uorescent Pseudomonads are now emerging. Here we describe the development of a non-solvent based process for the recovery of mcl-PHAs from the biomass. This ®rst paper addresses a procedure to solubilize the biomass, so that it can be separated from the particulate mcl-PHA. The solubilization procedure, involving heat, protease and detergent, leaves the peptidoglycan intact, which facilitates the separation. The purity of the resulting mcl-PHA exceeds 95%. In a subsequent paper, we utilize the solubilization procedure in a downstream process and we discuss the economics of the corresponding mcl-PHA production.

No abstract

Medium-chain-length poly(hydroxyalkanoates) (mcl-PHAs) are storage polyesters accumulated by¯uor-escent pseudomonads, which are currently receiving much attention because of their potential as biodegradable and renewable elastomers. Owing to their amorphous character, these biopolymers can ideally be handled as latices. The present paper describes the development of a nonsolvent based process for the recovery of mcl-PHAs. Via solubilization of the biomass and subsequent ®ltration, this process yields a latex as a ®nal product. From a preliminary economic evaluation, it was estimated that it should be feasible to produce mcl-PHA by this route at an ultimate minimum price of 5 US$ á kg ±1 .

We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to 25 mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two-dimensional system of electron spins. We approach the sample with a 3.43 μm-diameter magnetic particle attached to an ultrasoft cantilever and measure the frequency shift and quality factor as a function of temperature and the distance. Using a recent theoretical analysis [J. M. de Voogd et al., arXiv:1508.07972] of the dynamics of a system consisting of a spin and a magnetic resonator, we are able to fit the data and extract the relaxation time T 1 = 0.39 ± 0.08 ms and spin density σ = 0.14 ± 0.01 spins per nm 2 . Our analysis shows that at temperatures 500 mK magnetic dissipation is an important source of noncontact friction.