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Oxygen transfer deficiencies in starch-based media.

S D Vlaev1, M Valeva

  • 1Laboratory of Biochemical Reactors, Institute of Chemical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl.103, 1113, Sofia, Bulgaria.

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Summary

Oxygen transfer is limited in viscous starch solutions during Bacillus licheniformis degradation. Higher agitation speeds can improve oxygen transfer rates (OTR) in these challenging conditions.

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Area of Science:

  • Biotechnology
  • Biochemical Engineering
  • Microbial Fermentation

Background:

  • Starch degradation by Bacillus licheniformis involves oxygen transfer.
  • High viscosity in fermentation media impedes oxygen transfer.
  • Bacillus licheniformis is a key microorganism for starch bioconversion.

Purpose of the Study:

  • To investigate the impact of viscosity and agitation on oxygen transfer rate (OTR).
  • To determine optimal conditions for Bacillus licheniformis growth in viscous media.
  • To identify strategies for enhancing oxygen supply during fermentation.

Main Methods:

  • Cultivation of Bacillus licheniformis in varying viscosity starch media.
  • Measurement of oxygen transfer rate (OTR) under different agitation speeds.
  • Analysis of the relationship between viscosity, agitation, and OTR.
  • Evaluation of dual impeller systems for improved mass transfer.

Main Results:

  • OTR decreased significantly below 0.3 gl(-1) h(-1) at viscosities above 5-10 mPa.s and agitation below 710 rev/min.
  • Increasing agitation speeds by 30-50% compensated for OTR reduction in viscosities ranging from 10 to 200 mPa.s.
  • Dual impeller configurations were identified as crucial for enhancing microbial growth.

Conclusions:

  • Oxygen transfer is a critical limiting factor in viscous media during Bacillus licheniformis starch degradation.
  • Optimized agitation speeds are necessary to maintain adequate OTR in high-viscosity fermentation.
  • Implementing dual impeller systems is recommended for improved microbial performance and growth.