The strain SPO1 producing 13g of 2-keto-L-gulonic acid (2KGA) per liter was isolated as a spontaneous mutant of Gluconobacter melanogenus IFO 3293. For the enhancement of 2KGA productivity, we did further strain improvement studies of the mutant.As a result, the mutant U13, producing about 60g of 2KGAper liter from 100g of L-sorbose per liter, was obtained. In addition, the mutant Z84, producing about 60 g of 2KGAper liter from 100 g of D-sorbitol per liter, was also obtained.During the fermentation from L-sorbose and D-sorbitol, 5 to 10g of L-idonic acid per liter was produced as a by-product, but L-idonic acid was converted to 2KGAbefore the end of fermentation.

A novel metabolite, LL-Z1272a epoxide, structurally related to ascochlorin, was isolated from the cultured mycelium of Ascochyta viciae J-29, a mutant derived from A. viciae Libert. The structure was elucidated on the basis of spectroscopic data. The epoxide is proposed to be enzymatically formed from LL-Z1272a and is a precursor of ascochlorin, an antiviral and antitumor antibiotic. The conversion of the epoxide to ascochlorin by cyclization of its farnesyl chain to a cyclohexanone ring is similar to that of squalene 2, 3-oxide to sterols. Unlike ascochlorin, the new metabolite had no growth inhibitory activity against Candida albicans in the paper-disc agar diffusion assay.

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A number of soil isolates belonging to the genus Trichoderma were found to produce isonitrins A, B, C and D and isonitrinic acids E and F, a new class of antibiotics characterized by the presence of isonitrile groups. Taxonomy of the producing organisms, fermentation, isolation and physicochemical and biological properties of isonitrins and isonitrinic acids are reported. Isonitrin A showedthe highest in vitro antimicrobial activities against gram-positive and negative bacteria and fungi. During the course of screening for new antibiotics, we found Trichoderma species capable of producing antibiotic complexes, designated as isonitrins A, B, C and D, and isonitrinic acids E and F, characterized by the presence of an isonitrile group. This report deals with the taxonomyof these species, fermentation studies, isolation and physicochemical and biological properties of isonitrins and isonitrinic acids. The results of structural studies on these antibiotics will be reported elsewhere.