Efficient production of polyhydroxyalkanoates (PHAs) from Pseudomonas mendocina PSU using a biodiesel liquid waste (BLW) as the sole carbon source

Figures & data

Fig. 1. Neighbour-joining phylogenetic tree constructed on the basis of the 16S rRNA gene sequence showing the phylogenetic relationships between Pseudomonas sp. PSU and its close relationship to other Pseudomonas species. The percentages of replicate trees in which the associated taxa were clustered together in the bootstrap test (1000 replicates) are shown next to the branches.

Table 1. Maximum cell growth, PHA production and PHA productivity produced from Pseudomonas mendocina PSU at various concentration of total glycerol in BLW.

Total glycerol concentration in BLW (g/L)	Maximum DCW (g/L)	Maximum PHA concentration (g/L)	Maximum PHA content (% DCW)	PHA productivity (g/L/h)
5	3.13 ± 0.07	1.88 ± 0.04	57.42 ± 2.28	0.052 ± 0.003
10	3.37 ± 0.09	2.47 ± 0.05	70.47 ± 3.40	0.069 ± 0.002
20	3.65 ± 0.10	2.59 ± 0.07	76.89 ± 2.31	0.072 ± 0.003
30	2.90 ± 0.04	2.37 ± 0.03	64.77 ± 2.07	0.066 ± 0.002
40	2.05 ± 0.04	0.96 ± 0.03	46.61 ± 2.80	0.027 ± 0.002
50	1.93 ± 0.08	0.58 ± 0.04	30.06 ± 5.15	0.016 ± 0.001

Table 2. Maximum cell growth, PHA production and PHA productivity produced from Pseudomonas mendocina PSU from three different nitrogen sources.

Nitrogen source	Maximum DCW (g/L)	Maximum PHA concentration (g/L)	Maximum PHA content (% DCW)	PHA productivity (g/L/h)
(NH4)2SO4	3.65 ± 0.10	2.59 ± 0.07	76.89 ± 2.31	0.072 ± 0.003
NH4NO3	3.28 ± 0.04	1.85 ± 0.03	56.40 ± 1.82	0.038 ± 0.005
(NH2)2CO (urea)	2.72 ± 0.10	1.32 ± 0.03	48.93 ± 3.73	0.028 ± 0.004

Table 3. Predicted and experimental values of the responses at optimal conditions.

Condition	Carbon to nitrogen (mole/mole)	Initial pH	Temperature (°C)	DCW (g/L)	PHA content (% DCW)	Carbon utilization (g/L)
Optimal	40.29	7.11	34.38	3.61	77.78	9.40
Modified	40	7.0	35	3.58  ± 0.09	77.27 ± 2.08	9.60 ± 0.20

Fig. 2. Time profile of cell growth, PHA accumulation, alginate production and substrate utilization by Psuedomonas mendocina PSU grown with MSM supplemented with 20 g/L of total glycerol in BLW with a C/N of 40 at 35 °C and initial pH 7.0 (optimal conditions for PHA production obtained from RSM). Each data point represents a mean value of three independent experiments and a vertical bar represents the standard deviation.

Fig. 3. PCR analysis of the SCL-PHA synthase gene (phbC) and MCL-PHA synthase gene (phaC) in Pseudomonas sp. 100 pb ladder (lane 1, left) lane 2–4 primers for phbC amplification were used²⁴ whereas lane 5–7 primers for phaC amplification were used^25,26 lane 2 and lane 5; Pseudomonas mendocina PSU against control e.g. Pseudomonas sp. USM 4-55 (lane 3 and lane 6) and negative control e.g. Burkholderia sp. USM (lane 4 and lane 7).

Fig. 4. ¹H-NMR spectrum of PHA produced from Pseudomonas mendocina PSU when grown with BLW and a schematic structure of the PHA.