Abstract: This invention relates to Streptomyces avermitilis lacking branched-chain amino acid transaminase activity, branched-chain 2-oxo acid biosynthetic activity and, optionally and preferably, avermectin B-O-methyl transferase activity, methods for preparation thereof, and use thereof to produce natural and non-natural avermectins from branched-chain fatty acid or branched-chain 2-oxo acid precursors. Such avermectins are useful as parasiticides.

Abstract: The process of this invention is directed to isolating or otherwise obtaining an olefinic macrolide producing microorganism which microorganism does not contain epoxidase enzyme activity. This invention also relates to a process for preparing said olefinic macrolide by fermenting a mutant microorganism lacking epoxidase activity, designated rosX herein, which mutant is obtained from the wild-type microorganism. This invention also relates to a rosX mutant of Micromonospora rosaria, and to any microorganism having the identifying characteristics thereof, said mutant also designated ATCC 55709. This invention also relates to a process for preparing repromicin, the compound of formula (II), ##STR1## by mutating a wild-type microorganism capable of producing rosamicin to produce a mutant microorganism lacking epoxidase activity such that repromicin is produced by said mutant microorganism.

Abstract: Streptomyces avermitilis lacking branched-chain amino acid transaminase activity and/or branched-chain 2-oxo acid dehydrogenase activity, methods for preparation thereof, and use thereof to produce natural and non-natural avermectins useful as parasiticides.

Abstract: Streptomyces avermitilis lacking branched-chain 2-oxo acid dehydrogenase activity and avermectin B O-methyltransferase activity, method for preparation thereof, and use thereof to produce natural and non-natural B avermectins useful as parasiticides.

Abstract: Streptomyces avermitilis lacking branched-chain 2-oxo acid dehydrogenase activity and avermectin B O-methyltransferase activity, method for preparation thereof, and use thereof to produce natural and non-natural B avermectins useful as parasiticides.

Abstract: Streptomyces avermitilis lacking branched-chain amino acid transaminase activity and/or branched-chain 2-oxo acid dehydrogenase activity, methods for preparation thereof, and use thereof to produce natural and non-natural avermectins useful as parasiticides.

Abstract: Streptomyces avermitilis lacking branched-chain amino acid transaminase activity and/or branched-chain 2-oxo acid dehydrogenase activity, methods for preparation thereof, and use thereof to produce natural and non-natural avermectins useful as parasiticides.

Abstract: Streptomyces avermitilis lacking branched-chain 2-oxo acid dehydrogenase activity and avermectin B O-methyltransferase activity, method for preparation thereof, and use thereof to produce natural and non-natural B avermectins useful as parasiticides.

Abstract: Non-natural demethylavermectins useful as parasiticides and process therefor.

Abstract: A mutant Streptomyces thermoviolaceus, NRRL 15615, elaborates a thermostable glucose isomerase in high yield, constitutively. The GI produced shows a negligible loss in activity when heated at 90.degree. C. in high fructose corn syrup for 5 minutes relative to the same treatment at 80.degree. C. The mutant microorganism produces about 1500 units of glucose isomerase per gram of dry weight cells in the absence of xylose.

Abstract: A mutant Streptomyces coelicolor, NRRL 15398, produces glucose isomerase constitutively at a level at least as great as the parent does inductively in common growth media. The isomerase can be effectively used to isomerize glucose to fructose in a continuous process using immobilized enzyme.