Solid and liquid waste utilization in fermentation process to get bacterial insecticide.

Proceeding of the 5th International Congress on Engineering and Food, 28 May and 3 June, 1989, Cologne, Federal Republic of Germany

Recent observations on bacterial insecticide production by semi-solid fermentation technique.

The practical use of entomopathogenic microorganism, to crop protection is possible when an industrial scale production of the organism is developed. That is the case of Bacillus thuringiensis (Bt), one of the most studied and commercially important entomopathogenic bacterium. In Brazil the feasibility of Bt production depends, to a large degree, on the cost at which this product can be obtained. So, the fermentation technology has to aim the production of new fermentation media and new fermentation processes to get such economical level. In search of new fermentation processes it was studied the production of Bt spores and gama-endotoxin in a low cost medium (using agroindustrial by-products) by the semi-solid fermentation in flasks. The fermented malt and the solid residues from pulp and paper industry could both be used as a complete medium for growth and sporulation of this bacterium. Furthermore, the humidification or the supplementation of the culture media with a low price mineral salt source increases the yield of the spores production. It was concluded that the semi-solid fermentation technique can be successfully used for Bt spores and gama-endotoxin production

Outlook on the use of semi-solid culture media for the production of Bacillus thuringiensis.

Based on the fact that wider use of Bacillus thuringiensis for the biological control of insect pests has been restricted by economic reasons, studies were initiated to explore the feasibility of producing Bt. endotoxin preparations using semi-solid fermentation with cheap components as substracts. Some agroindustrial by-products including solid residue from paper industry, residual fermented malt from beer industry, and a special kind of meal obtained from residual cookies and biscuits of bakery industry, were investigated for their abilities to support Bt. growth and spore production. The technique was based upon the employment of semi-solid type of fermentation in erlenmeyers whose culture medium was composed by each residue separated, or by the combinatio n of two residues. The incubations was done at 30. C., with one hand-shaking each day, and spore counts and pH measurement were done until the seventh day. The semi-solid process used takes nearly 168 hours to produce 10 10 - 10 13 spores/g. The submerged fermentation results are nearly 10 9 - 19 10 spores/ml, in about 48-71 hours. Economic studies are conducted to determine the advantageous process, but the low cost of residues, the availability of them in Brazil, the technological aspects of production in small scale in some regions of the country, seem to be sufficient reasons to adopt the semi-solid fermentation process for Bacillus thuringiensisi production

Produção de inseticida biológico com Bacillus thuringiensis.

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