Abstract

The impact of formulation and desiccation on the shelf life of phosphate (P)-solubilising microorganisms is often under-studied, particularly relating to their ability to recover P-solubilisation activity. Here, Penicilllium bilaiae and Aspergillus niger were formulated on vermiculite (V) alone, or with the addition of protectants (skimmed milk (V + SM) and trehalose (V + T)), and on sewage sludge ash with (A + N) and without nutrients (A), and dried in a convective air dryer. After drying, the spore viability of P. bilaiae was greater than that of A. niger. V formulations achieved the highest survival rates without being improved by the addition of protectants. P. bilaiae formulated on V was selected for desiccation in a fluidised bed dryer, in which several temperatures and final water activities (aw) were tested. The highest spore viability was achieved when the formulation was dried at 25 degrees C to a final aw > 0.3. During three months' storage, convective air dried formulations were stable for both strains, except in the presence of skimmed milk for P. bilaiae which saw a decrease in spore viability. In the fluidised bed-dried formulations, when aw > 0.3, the loss in viability was higher, especially when stored at 20 degrees C, than at aw < 0.1. P-solubilisation activity performed on ash was preserved in most of the formulations after desiccation and storage. Overall, a low drying temperature and high final aw positively affected P. bilaiae viability, however a trade-off between higher viability after desiccation and shelf life should be considered. Further research is needed to optimise viability over time and on more sustainable carriers.

Keywords

Phosphate solubilising microorganisms; Convective air drying; Fluidized bed drying; Sewage sludge ash; Vermiculite; Shelf-life

Published in

Journal of Microbiological Methods
2018, Volume: 150, pages: 39-46
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Håkansson, Sebastian

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

SDG2 Zero hunger


UKÄ Subject classification

Microbiology


Publication identifier

DOI: https://doi.org/10.1016/j.mimet.2018.05.012

Permanent link to this page (URI)

https://res.slu.se/id/publ/95982