Core-shell encapsulation formulations to stabilize desiccated Bradyrhizobium against high environmental temperature and humidity

Kelly G Aukema, Mian Wang, Beatriz de Souza, Sophie O'Keane, Maia Clipsham, Lawrence P. Wackett, Alptekin Aksan

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Engineered materials to improve the shelf-life of desiccated microbial strains are needed for cost-effective bioaugmentation strategies. High temperatures and humidity of legume-growing regions challenge long-term cell stabilization at the desiccated state. A thermostable xeroprotectant core and hydrophobic water vapour barrier shell encapsulation technique was developed to protect desiccated cells from the environment. A trehalose core matrix increased the stability of desiccated Bradyrhizobium by three orders of magnitude over 20 days at 32°C and 50% relative humidity (RH) compared to buffer alone; however, the improvement was not deemed sufficient for a shelf-stable bioproduct. We tested common additives (skim milk, albumin, gelatin and dextran) to increase the glass transition temperature of the desiccated product to provide further stabilization. Albumin increased the glass transition temperature of the trehalose-based core by 40°C and stabilized desiccated Bradyrhizobium for 4 months during storage at high temperature (32°C) and moderate humidity (50% RH) with only 1 log loss of viability. Although the albumin-trehalose core provided exceptional protection against high temperature, it was ineffective at higher humidity conditions (75%). We therefore incorporated a paraffin shell, which protected desiccated cells against 75% RH providing proof of concept that core and shell encapsulation is an effective strategy to stabilize desiccated cells.

Original languageEnglish (US)
Pages (from-to)2391-2400
Number of pages10
JournalMicrobial biotechnology
Issue number9
StatePublished - Sep 2022

Bibliographical note

Funding Information:
We acknowledge funding from the University of Minnesota Biotechnology Demonstration Grant and BASF. We thank Toan Van Pho and Ted Deisenroth for helpful discussions and feedback. We thank Mike Freeman for the use of his biosafety cabinet.

Publisher Copyright:
© 2022 The Authors. Microbial Biotechnology published by Society for Applied Microbiology and John Wiley & Sons Ltd.


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