Folia Microbiol. 39 (6), 576-578 (1994) Suitability of Some Local Agro-Industrial Wastes as Carrier Materials for Cyanobacterial Inoculant M.H. ABD-ALLA and A.A. ISSA Botany Departmen4 Faculty of Science, Assiut University,Assiu4 Egypt Received August 12, 1994 ABSTRACT. Survivaland nitrogenase efficiencyof Nostoc commune and N. austinii were evaluated monthly in four carrier materials (sugarcane bagasse,wheat straw, wheat bran and peat) at 10, 30 and 40 ~ Survival, as well as nitrogenase activity, of both species was much better in peat, followed by wheat bran, sugarcane bagasse than in wheat straw at 10 and 30 ~ up to three months, the activity of N. commune being better than N. austinff. None of the materials tested was found to be superior to peat as carrier of Nostoc species but the results indicated that wheat bran and sugarcane bagasse can be used as inoculant carriers with relative success. Storage of inoculants in these carriers is feasibleat 30 ~ up to three months. Inoculation of plants with nonsymbiotic rhizosphere microorganisms for crop improvement has become a centre of interest, there having been various attempts to create artificial symbiosis between nonleguminous plants and nitrogen-fixing cyanobacteria (Gusev et al. 1986; Omar and Abd- Alla 1994; Abd-Alla et al. 1994) and thus to reduce the demand for nitrogenous fertilizers. As pot trials indicated that a commercially available soil carrier inoculant (cyanobactcria) can increase the growth of wheat (Abd-Alla et al. 1994), we tried to find a suitable carrier for the production of the appropriate inoculant. The carrier generally used in the formulation of commercial bacterization preparations is wet peat. However, suitable peat is not available in many developing countries. Thus, alternate materials that support a large number of viable microorganisms for extended periods of time are needcd. A synthetic carrier would have the advantage over natural materials in not displaying the variability that most natural material have (Dommergues et al. 1979). Thus, a synthetic carrier may be useful as a standard against which to compare natural, less uniform, materials, such as peat. In this study we determined the survival of two species of Nostoc, viz. N. commune and N. austinii, in three different carrier materials that are easily available in many developing countrics (sugarcane bagasse, wheat straw and wheat bran in addition to peat). Since inoculants are often storcd at room temperature, survival at 30 ~ was evaluated in this study, lnoculants are sometimes subjected to very high temperatures; for example, they are often left in the hot sun or stored in hot storage sheds. Therefore, high storage temperature (40 ~ was tested to determine whether Nostoc species can bc stored at high temperature in any of the carrier materials evaluated. MATERIALS AND METHODS Organisms. Two species of nitrogen-fixing cyanobactcria, Nostoc commune VAUCIIER and N. austbtff /~IARTIN and WAYATI', were grown in a modified Watanabe medium (EI-Nawawy et aL 1958) at 25 ~ under continuous illumination (400 Ix). Seven-day-old axenic culture was mixed and homogenized (66.6 Hz). The starting inoculum was adjusted to contain 105 hormogonia, each hor- mogonium consisting of approximately 5-6 cells. Preparation of local carriers. Wheat bran, wheat straw and sugarcane bagasse were examined during the study as potential carriers. Peat was used as a control. All the carriers were finally ground to pass a 60-mesh screen and their pH was adjusted to 6.8. The carrier materials were mixed with a modified Watanabe medium added at a rate of 40 % (V/W) in case of peat, wheat straw and sugar- cane bagasse and 20 % in the case of wheat bran (due to its low adsorptive capacity). Batches of 100 g each of treated carrier material were distributed in 1-L Erlenmeyer flasks and sterilized by steaming in the autoclave (121 ~ 20 min) on three successive days. Each flask was inoculated under aseptic conditions with 20 mL of 7-d-old culture of one Nos- toc species. Then the inoculants were incubated for three months at 10, 30 or 40 ~ The number of viable Nostoc in each carrier was determined monthly by plate counts as well as the efficiency of nitro- genase (EC 1.18.6.1) of the same sample were determined as described by Abd-Alla et al. (1~)4).