Agroindustry by-products as a carrier resource for plant-growth-promoting rhizobacterium, Bacillus subtilis

The traditional carriers viz., lignite and peat used in the biofertiliser industry are non-renewable, costly, non eco-friendly and have very limited reservoirs in India. Therefore, the present work in this paper was undertaken to check and evaluate whether the agroindustry by-products, viz., peanut shells, corn cobs, sawdust, paddy husk and pressmud, can be used as alternatives to the traditional carriers. Evaluation of the carriers was done by studying the survival of Bacillus subtilis at 28, 37 and 45?°C for a period of 3?months on a weekly basis by the viable plate count method. Physico-chemical characteristics of the agroindustry by-products showed that paddy husk has pH 6.66, 6.65?% (w/w) moisture content, 0.31 % (w/w) ash content, potassium 0.037?% (w/w) and other element content such as Co, Rb, Ag, Hg, Bi and Th is more as compared to that in lignite. The viable count of Bacillus subtilis was highest in paddy husk at 28 and 37?°C, which was 2.458?×?10⁵ and 2.470?×?10⁵ cfu/g, respectively. Thus, paddy husk is found to be an alternative carrier to lignite which is very cheap, renewable, eco-friendly, more easily available and is a very clean technology. Since it is the by-product of the agroindustry, its use as a carrier will give a value-added product and also protect the bacterial cells from desiccation.