Biodegradable latexes from animal-derived waste: Biosynthesis and characterization of mcl-PHA accumulated by Ps. citronellolis

Background: mcl-PHA biosynthesis by Pseudomonas citronellolis from tallow-based biodiesel as inexpensive carbon feed stock was accomplished. Fermentation protocols, kinetic analysis, an efficient product recovery strategy, and a detailed product characterization are presented. Results: A maximum specific growth rate, mu(max) of 0.10 and 0.08 h(-1), respectively, was achieved in two different fermentation set-ups. Volumetric productivity for mcl-PHA amounted to 0.036 g/L h and 0.050 g/L h, final intracellular PHA contents calculated from the sum of active biomass and PHA to 20.1 and 26.6 wt.%, respectively. GC-FID analysis showed that the obtained biopolyester predominantly consists of 3-hydroxyoctanoate and 3-hydroxydecanoate, and, to a minor extent, 3-hydroxydodecanoate, 3-hydroxynonanoate, 3-hydroxyhexanoate, and 3-hydroxyheptanoate monomers. This was confirmed by H-1- and C-13 NMR, also evidencing the occurrence of low quantities of unsaturated and 3-hydroxyvalerate building blocks. High purity of the recovered materials was proofed by elemental analysis. Regarding the results from thermogravimetric analysis, differential scanning calorimetry and molecular mass determination, results were in a range typical for this type of PHA (1st fermentation: decomposition temperature T-d = 296 degrees C, peak of melting range T-m = 48.6 degrees C; glass transition temperature T-g = -46.9 degrees C, degree of crystallinity X-c = 12.3%, M-w = 66,000, M-n = 35,000, dispersity index P-i = 1.9; 2nd fermentation: T-d = 295 degrees C, T-m = 53.6 degrees C, T-g = -43.5 degrees C, X-c = 10.4%, M-w = 78,000, M-n = 196,000, P-i = 2.5). (C) 2013 Elsevier Ltd. All rights reserved.