Solid-state Co-cultivation of Bacillus subtilis, Bacillus mucilaginosus, and Paecilomyces lilacinus Using Tobacco Waste Residue

Agro-industrial wastes are excellent sources for solid-state culture to produce spores of microorganisms, whereas microbial co-cultivation is not fully exploited in solid-state culture. In this work, the co-cultivation of different strains of Bacillus subtilis, and three microbes of B. subtilis, Bacillus mucilaginosus, and Paecilomyces lilacinus was studied using a solid medium only composed of water and tobacco waste residue after extraction of nicotine and solanesol. The influences of matrix thickness, moister, temperature, and ratio of three microbes in seed on the cell growth and spore formation were studied. The maximum viable cells and spores of each microbe reached 10(13) cfu/g when cultured alone at 30 degrees C in a medium containing 58.3% moisture. Co-cultivation of microbes stimulated cell growth and maximum viable cells of each microbe reached 10(14) cfu/g, while spore production was inhibited and decreased to 10(11) cfu/g. With decreasing amount of P. lilacinus in seed, total amount of spores was increased. When the seed with a ratio of 6:3:1 for B. mucilaginosus, B. subtilis, and P. lilacinus was inoculated, the total amount of spores reached 4.14 x 10(12) cfu/g and the ratio was 1.7:0.7:1. These results indicate the potential of solid-state cultivation in the high production of spores from tobacco waste residue at low cost.