title: Pulsed feeding during fed-batch fungal fermentation leads to reduced viscosity without detrimentally affecting protein expression.
abstract: The goal in this study was to determine if pulsed addition of substrate could be used to alter filamentous fungal morphology during fermentation, to result in reduced broth viscosity. In all experiments, an industrially relevant strain of Aspergillus oryzae was grown in 20-liter fermentors. As a control, cultures were fed limiting substrate (glucose) continuously. Tests were performed by altering the feeding strategy so that the same total amount of glucose was fed in repeated 300-s cycles, with the feed pump on for either 30 or 150 s during each cycle. Variables indicative of cellular metabolic activity (biomass concentration, oxygen uptake rate, base consumed for pH control) showed no significant difference between continuous and pulse-fed fermentations. In addition, there was no significant difference between total extracellular protein expression or the apparent distribution of these proteins. In contrast, fungal mycelia during the second half of pulse-fed fermentations were approximately half the size (average projected area) of fungi during fermentations with continuous addition of glucose. As a result, broth viscosity during the second half of pulse-fed fermentations was approximately half that during the second half of continuous fermentations. If these results prove to be applicable for other fungal strains and processes, then this method will represent a simple and inexpensive means to reduce viscosity during filamentous fungal fermentation.
authors.affiliation: Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA.
authors.forename: Swapnil
authors.initials: S
authors.lastname: Bhargava
authors.forename: M P
authors.initials: MP
authors.lastname: Nandakumar
authors.forename: Anindya
authors.initials: A
authors.lastname: Roy
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Wenger
authors.forename: Mark R
authors.initials: MR
authors.lastname: Marten
mesh_terms: D001236:Aspergillus oryzae / Q000254:growth & development* / Q000378:metabolism*; D019149:Bioreactors; D018929:Cell Culture Techniques / Q000295:instrumentation / Q000379:methods*; D002478:Cells, Cultured; D005240:Feasibility Studies; D005656:Fungal Proteins / Q000096:biosynthesis*; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism; D010507:Periodicity; D011786:Quality Control; D012212:Rheology / Q000379:methods; D012680:Sensitivity and Specificity; D014783:Viscosity
chemical_list: D005656:Fungal Proteins; D005947:Glucose