[A statistical method for the determination of the yield correlation of antibiotic-producing microorganisms].
The antibiotic yields of industrial selectants must be checked at several steps of cultivation. Here the question arises whether the activities at the different levels of cultivation are correlated. The common coefficient of correlation cannot be used because repeated determinations of the yield at one selectant result in different values. In order to have only one fixed value per selectant we define the mean value around which the observed values are varying. But these mean values cannot be observed. Thus, an adequate method of correlation similar to that in Guiard and Herrendörfer (1977) was used. The method is demonstrated in two examples: With selectants of Streptomyces noursei for streptothricin titers in 20 ml- and 20 l-cultures as well as with selectants of Penicillium chrysogenum for potency indices in surface cultures and penicillin titers in 50 ml submerged cultures, respectively. In both cases the coefficients of correlation were above 0.7.
Development and evaluation of a potency index screen for detecting mutants of Penicillium chrysogenum having increased penicillin yield.
U.v.-treated conidia of an industrial strain of Penicillium chrysogenum were spread on a growth-limiting agar medium. Colonies arising from the survivors were surrounded with a spore suspension of Bacillus subtilis to which penicillinase had been added. After appropriate incubation, discrete zones of bacterial inhibition, with sizes limited by the penicillinase, appeared around each colony. Using the criterion of potency index (diameter of inhibition zone divided by diameter of colony) strains were selected that subsequently gave improved penicillin production in shake-flasks. The technique also ranked correctly four industrial strains in order of their known penicillin-producing capacity. Employing three operators, 5000 isolates could be screened in each experiment and approx. 15000 strains could be screened in a month.
Instrumentation and Automated Photometric Titration Procedure for Total Acidity Determination in Red Wine Employing a Multicommuted Flow System
An automated procedure for photometric titration of red wine and associated instrumentation is described. The procedure was based on the flow-batch approach implemented employing multicommutation. The photometric detection was carried out using a homemade LED-based photometer. The mixing device, LED, and photodetector were attached to the titration chamber in order to form a compact and small-sized unit. The flow system comprised an automatic injector and three-way solenoid valves, which were controlled by a microcomputer through an electronic interface card. The software, written in Quick BASIC 4.5, was designed with abilities to accomplish all steps of the titration procedure including data acquisition and real-time processing to decide about the course of titration in the following step and so forth, until the titration endpoint was reached. The usefulness of the proposed titration system was demonstrated by analyzing red wine samples. When results were compared with those obtained using the AOAC reference method, no significant difference was observed at the 95% confidence level. A relative standard deviation of ca  2% (n=9 ) was obtained when processing a typical red wine sample containing 7.3 gl -1 total acidity expressed as tartaric acid.