Archaeal Production of Polyhydroxyalkanoate (PHA) Co- and Terpolyesters from Biodiesel Industry-Derived By-Products

Table 1

Maximum specific rates, yields, polymer productivity, and polymer characterization of different fermentations of H. mediterranei.

Maximum specific rates	F1^a	F2^b	F3^c	PHBHV4HB from whey and γ-butyrolactone [32]^d	PHBHV from whey [32]^d	PHBHV from rice bran [29]^e	PHBHV from glucose [28]^f	PHBHV from glucose [26]^g
μmax[1/h]	0.10	0.06	0.20	0.14	0.10	0.098	0.09	~0.10
𝜋max,1 [g/gh]; early prod. Phase	0.03	0.04	0.08	0.23	0.15	n.r.	n.r.	0.06
𝜋max,2 [g/gh]; late prod. Phase	0.02	0.02	0.01	0.01	0.11	n.r.	n.r.	~−0.006
Yields
Y (PHA/carbon source) [g/g]	0.37	0.19	0.16	0.20	0.29	n.r.	n.r.	0.26
max. protein [g/L]	5.0	5.5	5.6	2.10	4.60	65.1	44.1	3.61
max. PHA [g/L]	13.4	16.2	11.1	14.7	12.20	77.8	41.7	5.13
PHA/CDM [%] (end)	—	—	—	—	—	55.6	48.6	58.7
PHA (PHA + biomass protein) [%] (end)	75.0	76.0	66.2	87.5	72.8	—	—	—
Productivity
Vol. productivity [g/Lh] (PHA)	0.12	0.12	0.10	0.14	0.11	0.65	0.36	~0.08^i; ~0.15^j
Polymer characterization
1st. Melting endotherm (𝑇𝑚1), [°C]	130.2	128.7	122.4	139.0	150.8	n.r.	134.8/131.2^k	n.r.
2nd. Melting endotherm (𝑇𝑚2), [°C]	140.6	138.8	137.1	140.0	158.9	n.r.	144.4/140.7^k	n.r.
Cold crystallization peak [°C]	67.2	64.5	64.3	n.r.	62.2	n.r.	64.0/−50.0^k	n.r.
Glass transition temperature [°C]	4.3	7.0	2.5	−2.0	6.0	n.r.	1.56/−0.68^k	n.r.
Onset of decomposition (𝑇𝑑) [°C]	~240	~280	~285	236	241	n.r.	n.r.	n.r.
3-HV/PHA [mol-%]	10	10	11-12	21.8	6–9	n.r.	10.7/12.3^k	n.r.
4-HB/PHA [mol-%]	—	—	5	5.1	—	n.r.	—	n.r.
𝑀𝑤 [kDa]	150	253	391	986	1057	n.r.	570/72^k	n.r.
Polydispersity index 𝑃𝑖 (𝑀𝑤/𝑀𝑛)	2.1	2.7	2.6	1.5	1.5	n.r.	1.22/1.44^k	n.r.

aProduction of P(HBHV) from pure glycerol.
bProduction of P(HBHV) from crude glycerol phase (CGP) from biodiesel production.
cProduction of PHBHV4HB from CGP and 𝛾-butyrolactone.
dProduction of PHBHV4HB from hydrolyzed whey lactose plus sodium valerate as additional 3HV precursor and 𝛾-butyrolactone.
e Production of P(HBHV) from extruded rice bran and extruded corn starch (1/8 g/g).
fProduction of P(HBHV) from glucose.
gUnder phosphate-limited conditions; polyester reported as “PHB;” according to today’s knowledge: P(HBHV). Values with “∼” refer to the fact that the authors of the present study estimated these values from the original data provided in Figure 1 of [26].
hdegradation of PHA during late phase of fermentation due to glucose limitation (batch set-up).
iEntire process.
jBefore glucose limitation.
kTwo fractions of copolyester with different 3HV molar fractions were isolated.
n.r.: Not reported.