title: Inexpensive fed-batch cultivation for high poly(3-hydroxybutyrate) production by a new isolate of Bacillus megaterium.
abstract: This research aimed at increasing the cell density and production of the homopolymer polyhydroxybutyrate (PHB) by Bacillus megaterium BA-019, using renewable and inexpensive bioresources as a substrate. A higher cell density and a greater PHB production level were obtained by using sugarcane molasses and urea as carbon and nitrogen sources, respectively. The limitation of nitrogen at a C/N molar ratio of 25 resulted in enhanced cell growth and PHB production in batch cultures. Fed-batch cultivation with the feeding nutrient composed of MSM with sugarcane molasses, urea and trace elements, and controlled by a pH-stat feeding control, lead to a significantly enhanced cell concentration and PHB production. The optimal feeding medium in this system required a higher total sugar concentration (400 g/l) and a C/N molar ratio of 10 mol/mol. Under these conditions the highest attained cell mass (72.6 g/l DW) and PHB content (42% of cell dry wt.) were achieved in a short cultivation time (24 h), leading to improved PHB productivity (1.27 g/l/h). However, dissolved oxygen was limiting and thus the system is likely to be suboptimal and capable of even further improvements to the PHB production rate.
authors.affiliation: Department of Microbiology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand. ksongsri@chula.ac.th
authors.forename: Songsri
authors.initials: S
authors.lastname: Kulpreecha
authors.forename: Atipol
authors.initials: A
authors.lastname: Boonruangthavorn
authors.forename: Boonyarit
authors.initials: B
authors.lastname: Meksiriporn
authors.forename: Nuttha
authors.initials: N
authors.lastname: Thongchul
mesh_terms: D001410:Bacillus megaterium / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors; D002244:Carbon / Q000378:metabolism; D005285:Fermentation; D006885:Hydroxybutyrates / Q000378:metabolism*; D007218:Industrial Microbiology / Q000379:methods; D008965:Molasses / Q000382:microbiology; D010100:Oxygen / Q000378:metabolism; D011091:Polyesters / Q000378:metabolism*; D014508:Urea / Q000378:metabolism; D000094122:Polyhydroxybutyrates
chemical_list: D002244:Carbon; D006885:Hydroxybutyrates; D010100:Oxygen; D011091:Polyesters; D014508:Urea; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates