Fig 1.
Effect of freezing-thawing treatment on the residual activity of lipase in the absence and presence of 50 mM and 100 mM 3HB.
*note: Statistical significance was tested using 2 sample t-test (Minitab), each sample was compared with control, statistically insignificant results are labeled by red.
Fig 2.
A) Viability of S. cerevisiae culture during freezing-thawing challenge in the presence of 3HB applied at 50 mM and 100 mM and in its absence B) Viability of the yeast culture exposed to repeated freezing-thawing in the presence of 3HB, trehalose and glycerol (all protectants were applied at 100 mM concentration) and in absence of a cryoprotectant. *note: Statistical significance was tested using 2 sample t-test (Minitab), each sample was compared with control, all the differences were found statistically significant.
Fig 3.
A) Viability of PHB-accumulating C. necator H16 and PHB non-accumulating C. necator PHB-4 exposed to repeated freezing-thawing challenge in the presence and absence of 100 mM 3HB. B) Viability of C. necator H16 and C. necator PHB-4 exposed to various sub-zero temperatures without addition of 3HB. *note: Statistical significance was tested using 2 sample t-test (Minitab). Presence of 3HB resulted in statistically significant increase in viability for both tested cultures and for all freezing-thawing cycles. Difference between viability of C. necator H16 and C. necator PHB–4 was statistically significant for all experimental conditions except for the initial 2 freezing-thawing cycles in absence of 3HB. In Fig 3B viability of C. necator H16 was compared with viability of C. necator PHB-4 for each temperature of incubation; statistically significant differences are labeled by asterisks.
Fig 4.
Cryo-SEM microphotographs of A) PHB non-producing C. necator PHB-4, B) PHB-accumulating cells of C. necator H16.
Fig 5.
Results of DSC analysis of centrifuged PHB-containing and PHB non-containing cultures of C. necator.
A) MTDSC thermograms, B) QiMTDSC thermograms.
Fig 6.
Results of dynamic TGA analysis of centrifuged PHB-containing and PHB non-containing cultures of C. necator.
A) Weight loss at a heating rate of 10°C/min in the interval 25–700°C, B) derivative weight loss as a function of residual water content (arrows indicate critical water content).
Fig 7.
Results of isothermal TGA analysis of centrifuged PHB containing and PHB non-containing cultures of C. necator.
A) Weight loss at 60°C, B) derivative weight loss as a function of residual water content (arrows indicate critical water content).