Exogenous Trehalose Improves Growth, Glycogen and Poly-3-Hydroxybutyrate (PHB) Contents in Photoautotrophically Grown under Nitrogen Deprivation.

Glycogen and poly-3-hydroxybutyrate (PHB) are excellent biopolymer products from cyanobacteria. In this study, we demonstrate that nitrogen metabolism is positively influenced by the exogenous application of trehalose (Tre) in under nitrogen-deprived (-N) conditions. Cells were cultivated photoautotrophically for 5 days under -N conditions, with or without the addition of exogenous Tre. The results revealed that biomass and chlorophyll- content of experienced enhancement with the addition of 0.003 M and 0.03 M Tre in the -N medium after one day, indicating relief from growth inhibition caused by nitrogen deprivation. The highest glycogen content (54.09 ± 1.6% (/) DW) was observed in cells grown for 2 days under the -N + 0.003 M Tre condition ( < 0.05), while the highest PHB content (15.2 ± 0.2% (/) DW) was observed in cells grown for 3 days under the -N + 0.03 M Tre condition ( < 0.05). The RT-PCR analysis showed a significant increase in and transcript levels, representing approximately 1.2- and 1.3-fold increases, respectively, in grown under -N + 0.003 M Tre and -N + 0.03 M Tre conditions. This was accompanied by the induction of enzyme activities, including glycogen synthase and PHA synthase with maximal values of 89.15 and 0.68 µmol min mg protein, respectively. The chemical structure identification of glycogen and PHB from was confirmed by FTIR and NMR analysis. This research represents the first study examining the performance of trehalose in promoting glycogen and PHB production in cyanobacteria under nitrogen-deprived conditions.