title: Influence of nitrogen source and pH value on undesired poly(γ-glutamic acid) formation of a protease producing Bacillus licheniformis strain.
abstract: Bacillus spp. are used for the production of industrial enzymes but are also known to be capable of producing biopolymers such as poly(γ-glutamic acid). Biopolymers increase the viscosity of the fermentation broth, thereby impairing mixing, gas/liquid mass and heat transfer in any bioreactor system. Undesired biopolymer formation has a significant impact on the fermentation and downstream processing performance. This study shows how undesirable poly(γ-glutamic acid) formation of an industrial protease producing Bacillus licheniformis strain was prevented by switching the nitrogen source from ammonium to nitrate. The viscosity was reduced from 32 to 2.5 mPa s. A constant or changing pH value did not influence the poly(γ-glutamic acid) production. Protease production was not affected: protease activities of 38 and 46 U mL(-1) were obtained for ammonium and nitrate, respectively. With the presented results, protease production with industrial Bacillus strains is now possible without the negative impact on fermentation and downstream processing by undesired poly(γ-glutamic acid) formation.
authors.affiliation: AVT. Biochemical Engineering, RWTH Aachen University, Worringer Weg 1, 52074, Aachen, Germany, lena.meissner@avt.rwth-aachen.de.
authors.forename: Lena
authors.initials: L
authors.lastname: Meissner
authors.forename: Kira
authors.initials: K
authors.lastname: Kauffmann
authors.forename: Timo
authors.initials: T
authors.lastname: Wengeler
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Mitsunaga
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Fukusaki
authors.forename: Jochen
authors.initials: J
authors.lastname: Büchs
mesh_terms: D000645:Ammonium Sulfate / Q000737:chemistry / Q000378:metabolism; D001407:Bacillus / Q000201:enzymology / Q000254:growth & development*; D001426:Bacterial Proteins / Q000096:biosynthesis*; D019149:Bioreactors; D003470:Culture Media; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism; D010100:Oxygen / Q000502:physiology; D010447:Peptide Hydrolases / Q000096:biosynthesis*; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis; D017680:Potassium Compounds / Q000737:chemistry / Q000378:metabolism; D014783:Viscosity
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D009566:Nitrates; D017680:Potassium Compounds; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D010447:Peptide Hydrolases; C023844:potassium nitrate; D010100:Oxygen; D000645:Ammonium Sulfate