Rubradirin is an antibiotic of complex chemical structure which is active vs. methicillin resistant staphylococci. Its development has been limited due to inadequate production yields. The incorporation of neutral resins into fermentations of Streptomyces achromogenes v. rubradiris, UC 8051 resulted in the enhanced production of rubradirin. Resins HP-20, HP-21, XAD-2, XAD-7 and XAD-16 were employed in flask and tank fermentations. The incorporation of these resins promoted 2- to 4-fold enhancements of the rubradirin activity produced in flask fermentations, and the incorporation of XAD-16 and HP-21 into tank fermentations promoted production titer increases greater than 5 fold.

A medium was developed to obtain maximum yields of extracellular amylase from Bacteroides amylophilus 70. Crude enzyme preparations, obtained by ammonium sulfate precipitation of cell-free broth, contained six amylolytic isoenzymes that were detected by isoelectric focusing and polyacrylamide gel electrophoresis. One of these amylases was purified by diethylaminoethyl-Sephadex A-50 ion-exchange chromatography and Sephadex G-200 gel filtration techniques. Some properties of the purified extracellular a-amylase were: optimum pH, 6.3; optimum temperature, 43°C; pH stability range, 5.8 to 7.5; isoelectric point, pH 4.6; molecular weight, 92,000 (by sodium dodecyl sulfatedisc gel electrophoresis); and sugars causing inhibition, cyclomaltoheptaose, cyclomaltohexaose, and aD -phenylglucoside. In addition, Ca2+ and Co2+ were strong activators, and Hg2+ was a strong inhibitor; all other cations were slightly stimulatory. Dialysis against 0.01 M ethylenediaminetetraacetic acid caused a 58% loss of activity that was restored to 92% of the original by the addition of 0.04 M Ca2+. The enzyme affected a blue-value-reducing-value curve characteristic of alpha-type amylases. The relative rates of hydrolysis of amylose, soluble starch, amylopectin, and dextrin were 100, 97, 92, and 60%, respectively; Michaelis constants for these substrates were 18.2, 18.7, 18.2, and 16.7 ,umol of D-glucosidic bond/liter, respectively. The enzyme degraded maize (corn) starch granules to some extent and had relatively little activity on potato starch granules. Digestion of starch in the rumen is essential to maximum utilization of feed grains by the ruminant. To gain an understanding of starch digestion in the rumen, attempts have been made to purify and characterize rumen amylases. At present, however, only three rumen amylases, produced by Streptococcus bovis (10, 33, 35), Clostridium butyricum (10, 35), and Bacteroides amylophilus (S. S. Rahman, Ph.D. thesis, University of British Columbia, Vancouver, 1970, Diss. Abstr. 32:77), have been partially characterized. B. amylophilus produces extracellular amylases and may play an important role as a starch digester in the rumen (9). This report presents data on the production, purification, and characterization of this amylase and defines its possible role in rumen starch breakdown. MATERIALS AND METHODS Organism and cultural conditions. The organism used in this study was B. amylophilus 70, kindly ' Joumal paper no. J-8471 of the Iowa Agriculture and

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LIST OF FIGURES 1. Procedure of purification of the extracellular maltase of Bacillus brevls. 2. Relationship between viable cell count (»^) and extracellular maltase production by 2* brevis B-4389 when 1.0% maltose was added at 0 hr 4 hr (0 0), and 8 hr (A-*) after inoculation. 3. pH-activity profile of a crude extracellular maltase preparation from 2* brevis B-4389. 4. Temperature-activity profile of a crude extracellular maltase preparation from brevis 344389. 5. Tençerature stability of a crude extracellular maltase preparation from I[. brevis B-4389, 6. Elution pattern from a Sephadex 6-200 column of the extracellular maltase from brevis B-4389. 7. pH-activity profile of the partially purified extracellular maltase from brevis B-4389. 8. Temperature-activity profile of the partially purified extracellular maltase from brevis B-4389. 9. Temperature stability of the purified maltase preparation from brevis 8^4389. 10. Molecular weight determination of the extra cellular maltase from brevis B-4389 by using Sephadex G-200 gel filtration, 11. Lineweaver-Burk plots of the extracellular maltase fran JB. brevis B-4389. 12. Chromatographic analysis of a maltose-^, brevis B-4389 maltase digest. 13. Chromatographic analysis of a 24 hr maltose-^ B-4389 maltase digests 14. Chromatographic analysis of an isomaltose-B-» 4389 maltase digest.

Bacillus brevis NRRL B-4389 produced extracellular maltase (a-glucosidase; EC 3.2.1.20) only in the presence of short a-1,4-glucosidic polymers, such as maltose and maltotriose. An optimum medium was developed; it contained 2.5% maltose, 0.5% nonfat dry milk, 0.4% yeast extract, and 0.01% CaCl2. The enzyme was produced extracellularly during the logarithmic phase of growth; no cellbound activity was detected at any time. Partial purification of the maltase was accomplished by using diethylaminoethyl cellulose batch adsorption, ammonium sulfate precipitation, and Sephadex G-200 gel filtration. Maltase, isomaltase (oligo-1,6-glucosidase), and glucosyltransferase activities were purified 20.0-, 19.1-, and 11.5-fold, respectively. Some properties of the partially purified maltase were determined: optimum pH, 6.5; optimum temperature, 48 to 50°C; pH stability range, 5.0 to 7.0; temperature stability range, 0 to 50°C; isoelectric point, pH 5.2; and molecular weight, 52,000. The relative rates of hydrolysis of maltose (G2), maltotriose (G3), G4, methyl-aD -maltoside, G40, dextrin, and isomaltose were 100, 22, 12, 10, 10, 8, and 5%, respectively; the Km on maltose was 5.8 mM; Dglucose, p-nitrophenyl-aD -glucoside, and tris(hydroxymethyl) aminomethane were competitive inhibitors; transglucosylase activity of the enzyme on maltose resulted in the synthesis of isomaltose, isomaltotroise, and larger oligosaccharides. Maltases (a-glucosidases; EC 3.2.1.20) presently play an important role in the industrial production of glucose syrups used by the food industry. To the present, only two extracellular maltases from bacteria have been characterized in detail (9, 29). It was the purpose of this study to isolate a bacterium that produced extracellular maltase, to maximize enzyme production, and to purify and characterize the maltase. MATERIALS AND METHODS Isolation and mutagenesis. Over 100 isolates capable of producing extracellular maltase were obtained from soil samples by using the screening procedure of Wang et al. (30). An isolate that produced the most maltase in shake culture was identified as Bacillus brevis (S. J. McWethy, Ph.D. thesis, Iowa State University, Ames, 1977). The isolate was subjected repeatedly to N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis (1). Conditions for mutagenesis were: 100 ,ug of N-methyl-N'-nitro-N-nitrosoguanidine per ml, pH 6.0 (0.05 M tris(hydroxymethyl)aminomethane [Tris]-maleate buffer), and 20 min of exposure at 35°C. Mutants were screened for extracellular maltase production (30), and a three-step mutant that produced elevated levels of maltase was selected for further study.