title: Investigation of the links between heterocyst and biohydrogen production by diazotrophic cyanobacterium A. variabilis ATCC 29413.
abstract: This work investigates the effect of heterocyst toward biohydrogen production by A. variabilis. The heterocyst frequency was artificially promoted by adding an amino acid analog, in this case DL-7-azatryptophan into the growth medium. The frequency of heterocyst differentiation was found to be proportional to the concentration of azatryptophan (0-25 µM) in the medium. Conversely, the growth and nitrogenase activity were gradually suppressed. In addition, there was also a distinct shortening of the cells filaments and detachment of heterocyst from the vegetative cells. Analysis on the hydrogen production performance revealed that both the frequency and distribution of heterocyst in the filaments affected the rate of hydrogen production. The highest hydrogen production rate and yield (41 µmol H2 mg chl a(-1) h(-1) and 97 mL H2 mg chl a(-1), respectively) were achieved by cells previously grown in 15 µM of azatryptophan with 14.5 % of heterocyst frequency. The existence of more isolated heterocyst has been shown to cause a relative loss in nitrogenase activity thus lowering the hydrogen production rate.
authors.affiliation: Low Carbon Economy (LCE) Research Group, School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300, Nibong Tebal, Seberang Prai Selatan, Pulau Pinang, Malaysia.
authors.forename: Siti Fatihah
authors.initials: SF
authors.lastname: Salleh
authors.affiliation: Low Carbon Economy (LCE) Research Group, School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300, Nibong Tebal, Seberang Prai Selatan, Pulau Pinang, Malaysia. chazlina@usm.my.
authors.forename: Azlina
authors.initials: A
authors.lastname: Kamaruddin
authors.affiliation: Low Carbon Economy (LCE) Research Group, School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300, Nibong Tebal, Seberang Prai Selatan, Pulau Pinang, Malaysia.
authors.forename: Mohamad Hekarl
authors.initials: MH
authors.lastname: Uzir
authors.affiliation: Low Carbon Economy (LCE) Research Group, School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300, Nibong Tebal, Seberang Prai Selatan, Pulau Pinang, Malaysia.
authors.forename: Khairiah Abd
authors.initials: KA
authors.lastname: Karim
authors.affiliation: Low Carbon Economy (LCE) Research Group, School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300, Nibong Tebal, Seberang Prai Selatan, Pulau Pinang, Malaysia.
authors.forename: Abdul Rahman
authors.initials: AR
authors.lastname: Mohamed
mesh_terms: D003470:Culture Media / Q000737:chemistry; D000458:Cyanobacteria / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D009591:Nitrogenase / Q000378:metabolism; D014364:Tryptophan / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D003470:Culture Media; C006657:7-azatryptophan; D006859:Hydrogen; D014364:Tryptophan; D009591:Nitrogenase
keywords: Azatryptophan; Cyanobacteria; Heterocyst; Hydrogen; Nitrogenase