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

Backgroundmcl-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.ResultsA maximum specific growth rate, μ_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 ¹H- and ¹³C 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 °C, peak of melting range T_m = 48.6 °C; glass transition temperature T_g = ?46.9 °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 °C, T_m = 53.6 °C, T_g = -43.5 °C, X_c = 10.4%, M_w = 78,000, M_n = 196,000, P_i = 2.5).