Upregulation of ACC deaminase gene in Bacillus velezensis UTB96 improved yield and shelf Life of Agaricus bisporus

Agaricus bisporus is globally a most extensively consumed species of edible mushrooms. Ethylene secreted by A. bisporus mycelium suppress the initiation of fructification. 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing bacteria decrease the content of ethylene by cleaving ACC produced by the A. bisporus hyphae to α-ketobutyrate and ammonia. This study evaluated the effect of various salts on the population of Bacillus velezensis UTB96 with ACC deaminase activity on button mushroom. The results indicated that CaCl₂, MnSO₄ and MgSO₄ salts increased significantly the bacterial population compared by control, among which the medium supplemented with CaCl₂ showed the highest number of living cells in the culture. Evaluation of ACC deaminase gene expression indicated that the highest level belonged to bacteria grown in medium containing CaCl₂ in comparison with control as the expression level of ACC deaminase was 20.9-fold upregulated comparing to the control. The assessment of the effect of each salt lonely, UTB96 cultured in LB and LB containing salts of mushroom indicated that yield was increased 23% and 18% in plots treated with UTB96 cultured in media supplemented, respectively, with CaCl₂ and MnSO₄, in comparison with control. Therefore, UTB96 grown in media supplemented with CaCl₂ has a potential use in mushroom production since the induction of ACC deaminase which results in decrease the level of ethylene and promote mushroom growth.