Patent GB-1133875-A (GB)
Title: Continuous microbiological processes involving filamentous micro-organisms
Inventor: ROSS NEIL GRANT
IPC: C12P1/00
Filed: 1966-07-20
Abstract: 1,133,875. Production of antibiotics and steroids by continuous fermentation process. A.P.V. CO. Ltd. 20 Oct., 1967 [20 July, 1966], No. 32618/66. Headings C2A and C2U. [Also in Division C6] A continuous fermentation process for the production of chemical substances comprises the aerobic cultivation of a normally filamentous micro-organism in a substantially vertical elongate fermentation zone, fermentable liquid containing nutrients being supplied to the fermentation zone and fermented product being withdrawn from the fermentation zone, and the micro-organism is aerated by means of bubbles of oxygen-containing gas flowing upwards from the bottom of the zone and is maintained in a particulate aeratable form viz. as particles of mycelium composed of aggregates of cells such that at least a large proportion of these cells is capable of being adequately oxygenated and therefore capable of normal aerobic metabolism. The rate of supply of nutrients or of growth-limiting nutrient is controlled so that the normally filamentous micro-organism is maintained in the particulate aeratable form. The aggregates have diameters less than 1 mm. and generally have the property, not possessed by the filamentous form to any significant extent, of being able to settle under the influence of gravity. The fermentation is conducted in a cylindrical fermenter having a ratio of length to diameter of at least 6: 1, preferably between 10: 1 and 30: 1, under heterogeneous steady state conditions (constant metabolic gradients) with either upward or downward flow of the fermenting substrate. Back-mixing is minimized by baffles, for example in a tower having an overall length of 305 cms. and an internal diameter of 10 cm. by five perforated (1À3 cm. diameter holes) stainless steel discs of about 7À6 cm. diameter mounted coaxially at equal intervals along a stainless steel rod. The oxygen-containing gas is admitted through a stainless steel sintered disc with a pore size of about 50 Á or a ceramic sintered disc of smaller pore size, down to 3 Á. The following genera and species of micro-organisms are particularly mentioned: Streptomyces niveus, S. fradiae, S. albogriseolus, S. rimosus and S. aureofaciens, Nocardia, Penicillium chrysogenum and P. notatum, Aspergillus niger, Septomyxa affinis, Curvularia lunata and C. prasadii, Cephalosporium and Rhizopus. An example is directed to the cultivation of Streptomyces niveus for the production of novobiocin. The cultivation took place in a cylindrical stainless steel tower under a pressure of 17 p.s.i. (gauge). During the first 7 days (no medium flow) the microorganism was observed to grow in its normal filamentous form. Within 2 days of the start of the flow of medium, some degree of conversion of the mycelium from the filamentous form to the particulate aeratable form had taken place. This conversion was substantially complete within about 7 days of the commencement of medium flow, during which time the particles became granular in appearance. A further example is directed to the cultivation of Septomyxa affinis initially as a mixture of both unicellular and filamentous forms. As the fermentation progressed, aggregates of cells (as defined above) were formed with diameters in the range 0À05-0À12 mm., some of which were star-shaped. Mention is made of the conversion of 6α-methylhydrocortisone acetate by Septomyxa affinis (pH 7-8) into 6α - methylprednisone.