High Aeration Rate Research Articles

Surfactin, a crystalline peptidelipid surfactant produced by [formula omitted][formula omitted]: Isolation, characterization and its inhibition of fibrin clot formation

Microbial biosurfactants have attracted the attention of researchers and companies for the last decades, as they are considered promising candidates to replace chemical surfactants in numerous applications. Although in the last years, considerable advances were performed regarding strain engineering and the use of low-cost substrates in order to reduce their production costs, one of the main bottlenecks is their production at industrial scale. Conventional aerobic biosurfactant production processes result in excessive foaming, due to the use of high agitation and aeration rates necessary to increase dissolved oxygen concentration to allow microbial growth and biosurfactant production. Different approaches have been studied to overcome this problem, although with limited success. A not widely explored alternative is the development of foam-free processes through the anaerobic growth of biosurfactant-producing microorganisms. Surfactin, produced by Bacillus subtilis, is the most widely studied lipopeptide biosurfactant, and the most powerful biosurfactant known so far. Bacillus licheniformis strains produce lichenysin, a lipopeptide biosurfactant which structure is similar to surfactin. However, despite its extraordinary surface-active properties and potential applications, lichenysin has been scarcely studied. According to previous studies, B. licheniformis is better adapted to anaerobic growth than B. subtilis, and could be a good alternative for the anaerobic production of lipopeptide biosurfactants. In this review, the potential and limitations of surfactin and lichenysin production under anaerobic conditions will be analyzed, and the possibility of implementing foam-free processes for lichenysin production, in order to expand the market and applications of biosurfactants in different fields, will be discussed.

6-Aminopenicillanic acid. I. 6-Aminopenicillanic acid in penicillin fermentations.

When a side-chain precursor was omitted from a penicillin fermentation, the yield of penicillin was diminished and 6-aminopenicillanic acid accumulated. In general, the conditions for 6-aminopenicillanic acid formation were similar to those for penicillin formation. Different requirements existed, however, with respect to aeration and the presence of precursor. During the growth phase, a high aeration rate favoured the formation of both the penicillin and 6-aminopenicillanic acid-producing systems. During the production phase, an oxygen transfer rate permitting the maximum respiration was required for maximum rate of penicillin formation. 6-Aminopenicillanic acid formation, on the other hand, was depressed under such conditions of aeration and the maximum rate of 6-aminopenicillanic acid formation by washed mycelium occurred with an oxygen transfer rate which limited respiration to approximately 60 % of maximum. A high aeration rate was necessary for efficient utilization of precursor for penicillin formation and under such conditions, the presence of precursor resulted in an increase in the total amount of penicillin nucleus produced in the fermentation.

ペニシリン醗酵に関する研究

The degree of varying the lactose-glucose ratio on penicillin yield was studied in submerged cultures. In shake flask culture, the yield of penicillin in corn steep liquor media was smaller when glucose was used as a main source of carbohydrate. Inferiority of glucose to lactose was due to the metabolic unbalance between carbohydrate and nitrogen-containing compounds resulting from its too rapid utilization, leading to an early setting in of mycelial autolysis. The superiority of lactose was associated with its slow rate of utilization as compared with glucose. However, at high agitation and aeration rate in 5l-jar culture, the use of high glucose concentration was advantageous with rapid, high penicillin yields when pH was adjusted at 7, 2 with sulfuric acid during the fermentation. Active penicillin synthesis was performed during the sugar starving period just after the rapid production of mycelium. This marked difference in yields between these two types of fermentations seemed to be attributed in part to the agitation and aeration.

The effect of aeration on the utilization of respiratory substrates by Penicillium chrysogenum in submerged culture.

SUMMARY: At high aeration rates in submerged culture, lard oil (mainly glycerides of oleic and stearic acids) may be utilized by Penicillium chrysogenum as a source of carbon in preference to carbohydrate. At relatively low aeration rates, carbohydrate serves as the principal carbon source. Enzymes involved in the utilization of lard oil appear to be synthesized by the growing mycelium, this synthesis being favoured by conditions of high aeration.

Antibiotic production by a species of Cephalosporium.

Summary: The antibacterial activity of a strain of a Cephalosporium sp. was found to be due to a number of antibiotics. One group of these, named Cephalosporins P, is soluble in organic solvents and active only against Gram-positive bacteria. The P antibiotic(s) is produced in good yield in deep culture in a medium comprising corn steep liquor and glucose at an initial pH of 6·3. A high aeration rate assisted by adequate stirring is essential. Submerged cultures 72 hr old form convenient inocula. Under optimum conditions with 2% (v/v) of such an inoculum the maximum titre is reached after 47–50 hr. at 24°, and thereafter falls.