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H2S bacteria of seafish flesh are weakly halophilic and require on average 1.68% NaCl according to statistical studies. Enumeration is optimal on PCA-H2S(a PCA medium supplemented with sulfur sources and increased NaCl concentrations) incubated at 25C. Total aerobic bacteria can be counted simultaneously on this medium. The proportion of H2S bacteria relative to total aerobic bacteria increased slightly during prolonged storage of the fish, but was highly variable. Models relating H2S bacterial counts to spoilage of fish are sigmoidal and showed that when the count exceeds 10,000 CFU/g, whole or filleted fish stored in ice at 0C are unfit for consumption. Shewanella putrefaciens accounted for 69% of the H2S bacteria at the fifth day of storage and 100% at the fifteenth.

H2S+ bacteria responsible for the degradation of sulfur-containing amino acids of fish muscle are currently little used to evaluate the microbiological pal quality of fish. Shewanella putrefaciens greatly predominates in this flora, and was therefore used to define a suitable culture method and medium. Inoculations by the Spiral surface method at 25C, with an incubation of 72h, gave the best counts on a medium containing two sources of sulfur (organic and inorganic) for H2S+ bacteria. The culture medium and the NaCl concentration were determinant in the evaluation of this flora. At present there is no standard medium which meets these requirements.

The total aerobic flora of seafish flesh is weakly halophilic, and requires on average 1.38% NaCl according to statistical studies. Enumeration is optimal on tryptone soya agar or on NaCl supplemented plate count agar (-H2S), incubated at 20 and 25C, respectively. Plate count agar (-H2S) was selected because it can also be used for enumeration of hydrogen sulfide-producing bacteria by degradation of sulfur-containing proteins, which are abundant in fish The models employed are sigmoidal. The initial bioburden is too great for there to be a lag phase during storage in ice at 0C. The models show that when the total aerobic microflora count exceeds 100,000 cfu/g, whole or filleted fish stored on ice at 0C are unfit for consumption.

Production of Bradyrhizobium japonicum cell concentrates by spray-drying in skim milk plus sucrose medium and the feasability of storing dried inocula over long periods were investigated. Storage of spray-dried cells under mild vacuum was equivalent to storage under nitrogen. Oxygen and ambient temperature were found detrimental for survival of dried cells. High initial cell concentration and storage under low relative humidities ( 10 9 cfu g -1 during at least a 25 week storage period) without altering the symbiotic properties of B. japonicum

The extracellular inulinase system of a strain of Arthrobacter sp. consists of a β-fructofuranosidase active on inulin raffinose and sucrose with a relative rate inulin/sucrose (I/S) of 0.2. Crude enzyme preparations were obtained by fractionation of the liquid culture at stationary phase of growth with ammonium sulphate. Purification was carried out by DEAE cellulose chromatography and ultrogel ACA 34. Only one protein band was observed by electrophoresis. The enzyme was stable at high temperatures and was active at neutral or slightly alkali pH. Fructose is liberated as the sole reaction product of inulin hydrolysis, suggesting that the enzyme was an exoinulinase. The Michaelis constant (calculated at 40°C and pH 6) was 0.25 × 10-2 mol/l for the inulin and 0.12 × 10-2 mol/l for sucrose. The enzyme was suitable for fructose production from root extracts of plants rich in polyfructosans or sucrose.