Nikkomycin production in pellets of Streptomyces tendae.

In previous submerged fermentation experiments mycelial suspensions of Streptomyces tendae were viscous and availability of oxygen limited the yield of nikkomycins (Nk), a complex of secondary metabolites which includes nucleoside-peptides with antibiotic activity. Increasing agitation improved oxygen transfer but consumed considerable power and shear-damaged cells. In this paper, cellular aggregates (pellets) were used to reduce viscosity and protect cells from shear. Under the conditions tested, specific productivity of S. tendae pellets increased with increasing size up to 1.4 mm diameter and then decreased. The maximal specific productivity of S. tendae pellets (44 mg Nk/g dry weight/h) occurred at a very low cell concentration. Pellet formation or high biomass concentration was required for the production of bioactive dipeptide and tripeptide Nks. It is speculated that accumulation of intermediates in large pellets activates the production of mature secondary metabolites.     

Pellet formation and cellular aggregation in Streptomyces tendae

In submerged cultures, Streptomyces tendae tended to form fluffy spherical pellets of the noncoagulative type. An increase in the average pellet size could be attained by decreasing any of the following: shear rate, pH, temperature, or inoculum size. Conditions leading to oxygen limitation tended to reduce the average pellet size and induced pulpy growth, whereas oxygen sufficiency seemed to induce pellet formation. Factors inducing pellet formation simultaneously increased cell wall hydrophobicity. It is therefore proposed that the main forces inducing cellular aggregation in S. tendae are hydrophobic interactions of cell walls, and these interactions are controlled by availability of dissolved oxygen.     

Microbial growth on peptones from fish industrial wastes

Industrial fish peptone was an excellent substrate for biomass production in solid and submerged fermentations. The maximal growth rates of several microorganisms were two to three times higher than those grown on beef (bacto)peptones and the final biomass concentrations were almost twice as great as those grown on beef peptones. Fish peptones did not increase the production of secondary metabolites relative to those produced on beef peptones in non-optimized media. Fish peptone has promising potential as a substrate for biomass production.     

Fermentation broth of Bacillus thuringiensis as a source of precursors for production of nikkomycins

Production of nikkomycins (nucleoside antibiotics inhibiting chitin synthesis) by Streptomyces tendae (ATCC 31160) was considerably enhanced by addition of fermentation wastes of Bacillus thuringiensis var. kurstaki (HD 263) to the basal soymannitol medium. Analysis of this fermentation broth for nucleic acid derivatives showed that they contained about 0·8 g/l of various nucleosides and bases (uracil 0·43 g/l; hypoxanthine 0·21 g/l; as well as uridine, cytosine and adenine).     

Nikkomycin production in pellets of Streptomyces tendae

S.E. VECHT-LIFSHITZ, Y. SASSON AND S. BRAUN. 1992. In previous submerged fermentation experiments mycelial suspensions of Streptomyces tendae were viscous and availability of oxygen limited the yield of nikkomycins (Nk), a complex of secondary metabolites which includes nucleoside-peptides with antibiotic activity. Increasing agitation improved oxygen transfer but consumed considerable power and shear-damaged cells. In this paper, cellular aggregates (pellets) were used to reduce viscosity and protect cells from shear. Under the conditions tested, specific productivity of S. tendae pellets increased with increasing size up to 1.4 mm diameter and then decreased. The maximal specific productivity of S. tendae pellets (44 mg Nk/g dry weight/h) occurred at a very low cell concentration. Pellet formation or high biomass concentration was required for the production of bioactive dipeptide and tripeptide Nks. It is speculated that accumulation of intermediates in large pellets activates the production of mature secondary metabolites.     

Biotechnological applications of image analysis: present and future prospects.

The current and potential biotechnological applications of image analysis and image processing systems are reviewed. Image analysis systems have proven to be highly versatile and efficient tools for assisting academic biotechnological research. It is expected that image analysis systems will allow more rapid and accurate quantification of numerous biotechnological analyses. There is, therefore, much scope for the implementation of image analysis/processing systems in a large variety of industrial and clinical applications.     

Mycelial morphology and metabolite production

Mycelial microorganisms are exploited extensively in the commercial production of a wide range of secondary metabolites. They can be cultured as free mycelia, as aggregated forms (pellets/flocs), or as artificially bound/entrapped cells, though problems are associated with the culture of each morphological type. Since the morphological type can strongly influence metabolite production, the methodology for inducing pellet formation, and the type of pellets produced are an important consideration for effective metabolite production.