Production of Characteristic Odors by Neurospora

We reported that Neurospora sp. ATCC 46892 produced a fruity odor, for which ethyl caproate may be responsible, I) but few studies have been done on odor production by other Neurospora strains. This study was aimed at examining the production of odors by several Neurospora strains. We examined 12 Neurospora strains, including the ATCC 46892 dscribed previously. I) Neurospora sp. T, which was newly isolated from beiju, a fermented food in Brazil, had been obtained from Dr. Satoh (Universidade Estadual de Campinas, Brazil) and was classified by us from its morphological characteristics. Other strains were purchased from the Institute for Fermentation, Osaka, Japan. These Neurospora strains were inoculated into 5% malt broth and grown aerobically at 30°C for several days in a 500-ml shaking flask. Then each culture was filtered through Miracloth (Calbiochem Corp.) or a microfilter (0.45/lm). Volatiles were extracted and analyzed. Two hundred and fifty ml of the filtrate obtained was saturated with NaCI and then 125 ml of ethyl acetate containing an internal standard, methyl caproate, was added to extract volatiles. After the mixture was shaken vigorously for one minute by a Mini-Beadbeater (Biospec Products), four microliters of the extract was analyzed by GC or GC-MS. GC was done with a Perkin-Elmer 8320B capillary gas chromatograph. The conditions were the same as described elsewhere3) with some modifications: column, a bonded fused silica capillary column, 15 m, 0.53 mm i.d., film thickness = 1.0 /lm; stationary phase, DB-WAX from J and W Scientfic Inc.; carrier gas, helium at 4.6ml/min (split ratio = 1/5); column temperature, kept at 70°C for 3 min, raised from 70°C to lOO°C at the rate of lOoC per min, from lOO°C to 230°C at the rate of 20°C per min and then kept at 230°C for 7.5min; injection port and detector temperature 250°C. GC-MS was done with a Hewlett Packard 5970B GCMS System. The conditions of gas chromatography were Table I. ODOR FORMATION BY VARIOUS Neurospora STRAINS The experimental details are given in the text.