Phosphate solubilisation, zinc oxide solubilisation and polyamine production
Yeast inoculum was prepared by cultivation in a 5 ml YPD broth (10 g l−1 yeast extract, 20 g l−1 peptone and 20 g l−1 dextrose) and the culture was incubated on a reciprocal shaker at 180 strokes/min at 28 ± 2 °C for 24 h. The inoculum density was adjusted to an optical density at 600 nm (OD600) of 0.10 and 3 μl was spotted onto Pikovskaya's agar (Zaidi et al. 2006), zinc oxide agar (Rokhbakhsh-Zamin et al. 2011), and Long Ashton decarboxylase (LAD) agar ( Cloete et al. 2009), and incubated at 28 ± 2 °C for 5 d. The phosphate and zinc oxide solubilisation efficiency (SE) was calculated as a ratio between the diameter of the halo zone and the diameter of the colonies.