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 1013 cfu/g when cultured alone at 30 °C in a medium containing 58.3% moisture. Co-cultivation of microbes stimulated cell growth and maximum viable cells of each microbe reached 1014 cfu/g, while spore production was inhibited and decreased to 1011 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 × 1012 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.
Keywords: Bacillus mucilaginosus; Bacillus subtilis; Paecilomyces lilacinus; Solid-state co-culture; Tobacco waste.