title: The influence of shear on the metabolite yield of Lactobacillus rhamnosus biofilms.
abstract: A tubular recycle bioreactor was employed to ensure homogeneous shear conditions on the biofilm surface. Superficial liquid velocities of 0.19 ms(-1), 0.37 ms(-1), 0.55 ms(-1) and 3.65 ms(-1) were used. The highest velocity resulted in negligible cell attachment (chemostat) while the ratio of attached-to-total cell mass escalated as the superficial velocity decreased. The lactic acid yield on glucose increased from 0.75 g g(-1) to 0.90 g g(-1) with declining shear while the corresponding acetoin yield on glucose decreased from 0.074 g g(-1) to 0.017 g g(-1). Redox analysis of the catabolites revealed a net consumption of NADH in the anabolism, while the extent of NADH consumption decreased when shear was reduced. This was attributed to the formation of more extracellular polymeric substance (EPS) at low shear conditions. A simplified metabolic flux model was used to estimate the EPS content of the biomass as a function of the shear velocity. Rate data supported the notion of increased EPS at lower shear.
authors.affiliation: University of Pretoria, Department of Chemical Engineering, Lynnwood Road, Hatfield, Pretoria 0002, South Africa.
authors.forename: Hendrik Gideon
authors.initials: HG
authors.lastname: Brink
authors.affiliation: University of Pretoria, Department of Chemical Engineering, Lynnwood Road, Hatfield, Pretoria 0002, South Africa. Electronic address: willie.nicol@up.ac.za.
authors.forename: Willie
authors.initials: W
authors.lastname: Nicol
mesh_terms: D000093:Acetoin / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors; D005947:Glucose / Q000378:metabolism*; D052201:Lacticaseibacillus rhamnosus / Q000502:physiology*; D009249:NADP / Q000378:metabolism
chemical_list: D009249:NADP; D000093:Acetoin; D005947:Glucose