Polyhydroxybutyrate solubility

Due to the differences between the physical structures of the intracellular native granules and extracellular denatured PHA, intracellular PhaZ is unable to hydrolyse extracellular PHA, and extracellular PhaZ cannot hydrolyse intracellular PHA [14]. The enzymatic degradation of P(3HB) is known as a heterogeneous reaction because the polyhydroxybutyrate (PHB) depolymerase is water-soluble, whereas the P(3HB) polymer is water-insoluble. Therefore, the enzymatic degradation of P(3HB) involves two steps, namely adsorption and hydrolysis. During adsorption, the enzyme is attached to the surface of P(3HB) via the binding domain of the polymer. This is followed by hydrolysis of the polymer chain at the active site of the enzyme [5]. 

A more recent biodegradable polymer is polyhydroxybutyrate-valerate copolymer (PHBV) from ICI Americas Inc.. These copolymers are produced through biochanical means. In fact, these natural thermoplastics are derived from bacteria. They are fully degradable in many microbial environments. Other biodegradable polymers include Konjac, a water-soluble polysaccharide produced by FMC Chitin, another polysaccharide that is insoluble in water and Chitosan, which is soluble in water. 

Various polymers have been successfully electrospun from solution, sol-gel suspension, or melt into ultrafine nanotibers. For example, as listed in Table 13.2, these polymers included nylon-6 [20, 21], polyacrylonitrile (PAN) [22, 23], polyethylene terephthalate (PET) [24], polyvinyl alcohol (PVA) [25], polystyrene (PS) [26, 27], polyvinylidene fluoride (PVDF) [28, 29], polyethersulfone (PES) [30], polyimides (PI) [31, 32], polyethylene oxide (PEO) [33], polyurethanes (PU) [34], polycarbonates (PC) [35], polycaprolactone (PCL) [36], polybenzimidazole (PBI) [37, 38], polyvinylpyrrolidone (PVP) [39], polytrimethylene terephthalate (PTT) [40], polyvinyl chloride (PVC) [41], polymethylmethacrylate (PMMA) [42], hydrox-ypropyl cellulose (HPC) [43], polyglycolic acid (PGA) [44], polyhydroxybutyrate (PHB) [45], cellulose acetate (CA) [46,47] and many more. To be used as filtration membranes, nanoflbers made of water-soluble polymers have to be further cross-linked after the electrospinning process. As polymers having different physical and... 

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