See the following articles. You may change the media composition favorable to Bacillus.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC400813/pdf/emboj00126-0024.pdf

http://herman.marc.usda.gov/sp2UserFiles/Place/36221500/cswq-0054-118437.pdf

HCN detection is done using filter papers (soaked in 0.5% picric acid in 2% sodium carbonate) placed on the lid of the petriplate. the bacterial culture is grown on TSY medium amended with glycine 94.4g/l). The plates were then sealed air-tight with Parafilm and incubated at 30°C for 48 h. A colour change of the filter paper from deep yellow to reddish-brown colour was considered as an indication of HCN production.

In the presence of free cyanide picric acid is reduced to coloured isopurpuric acid, the colour developed is directly proportional to free cyanide

Please clarify how to place picrate filter paper on the lid..should it be touching the media or in the inverted plate lid??