Spore inoculum

The production of the pectinases in the sohd substrates composed of wheat bran, rice bran and rice husk (6 12 2) was considerably very low. The spore inoculum of Rhizopus sp. 26R was prepared on raw cassava starch agar which the cost estimation was US 1.0 per 1 litre. Wheat bran, rice bran and rice husk were approx. US 64 per 50 kg. The total cost of the production of pectinases from Rhizopus sp. 26R in the sohd substrates, when considered only on the substrates was estimated to be only US 178 - 180 for 10 million units of crude pectinase. 

Cost of the enzyme production in solid substrate was estimated to be US 180 for 10 million units of crude pectinase. This price included the production of fungal spore inoculum. This production of pectinases from Rhizopus sp. 26R using agricultural wastes as solid substrates was one of the way to utilize agricultural wastes to value-added products and the cost of the enzyme production was very reductive. 

Shake flask studies were carried out at 39°C in 125-ml Erlenmeyer flasks containing 40 ml of medium (180 rpm, 2.5 cm dia cycle). The carbon nitrogen ratio was varied by increasing or decreasing the diammonium tartrate supply, and Mn(II) added as specified. A spore inoculum was used (0.5 to 1.0 10 spores/ml final concentration). 

Cell Growth. Mycelial pellets of P. chrysosporium (ATCC 24725) were produced under nitrogen limited culture conditions at 37°C using a spore inoculum (36). The pellets were grown for 72 hr at 150 rpm after which they were concentrated fourfold by decanting excess medium. They were used for reduction experiments after a 24 hr activation period (37°C, 50 rpm, under 100% O2 atmosphere). 

Table IV. Results of Experiments with 6. Subtilis Var. Niger Spores Inoculum...

Table V. Results of Experiments on Raw Sewage with 6. Anthracis Spores Inoculum...

Cultures can be inoculated with a spore suspension, or with a small volume of cellulose culture containing mycelium. Enzyme yields are equal with either inoculum, but the mycelial inoculum usually gives more rapid growth and earlier enzyme development. Spore inoculum is usually more convenient for shake flask experiments. 

Spore inoculum, shake flask cultures grown 18 days at 29 °C., 1.0% Solka Floe. Filter paper activity = mg. glucose produced in standard test, see text. 

Spore inoculum, shake flask experiment, grown 18 days at 29°C. 

Papagianni M, Mattey M. Morphological development of Aspergillus niger in submerged citric acid fermentation as a function of the spore inoculum level. Application of neural network and cluster analysis for characterization of mycelial morphology. Microb Cell Factories 2006 5 3. 

Generally in large-scale SSF, a high inoculum density is used to reduce the risk of contamination and to produce the desired level of product in a shorter duration. If the inoculum has to be generated in a liquid medium, large-scale fermenters should be used. In many cases, spore inoculum is preferred over inoculum generated in a liquid medium because of ease of uniform mixing of the spore with the moist solid substrate. 

In the various investigations discussed below, unless stated otherwise, a spore inoculum of A. flavus was used and the organism was grown aerobically in stationary culture. 

Toxicity of TNT to P. chrysosporium has also been demonstrated. Spiker et al. (79) observed little fungal growth from a spore inoculum in the presence of 20 ppm TNT. They also observed that when TNT was added to pregrown mycelia (7 days after inoculation) in fresh media, up to 100 ppm TNT could be degraded but further fungal growth was inhibited by 65 ppm TNT. In these studies inhibition of mycelial growth was used as the measure of toxicity. 

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