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Addition of iron (as a solution of reagent grade FeCl2, up to 20 mmol/1) to a methanogenic culture utilizing acetic acid markedly increased conversion of acetic acid to methane. The optimum soluble iron concentration was between 0.2 and 2 mM, with higher concentrations becoming slightly less stimulating. Most of the iron added precipitated within days after addition (mostly as ferrous carbonate or phosphate). Conversion of acetic acid to methane in liquid from municipal sewage digesters and from laboratory food processing waste digesters was also increased markedly by addition of iron. Results indicate that optimization of the conversion of acetic acid to methane in methanogenic fermentations requires soluble iron levels many times higher than those often required for maximum growth and activity in microbial cultures.

A new species of Clostvidium isolated from a methanogenic cellulose-enrichment culture of sewage sludge is described. The colonies produced by these bacteria were white, circular, and convex with smooth margins. The cells were straight, spindle-shaped rods, 0.6 by 3.0 pm in size. They were gram negative and nonmotile, and they formed round, terminal spores. A wide variety of carbohydrates was fermented by this mesophilic anaerobe. The major fermentation products were acetic acid, hydrogen, carbon dioxide, and ethanol. The deoxyribonucleic acid base composition was 28 mol% guanine plus cytosine. The name Clostridiurn saccharolyticurn is proposed for this new species on the basis of its broad saccharolytic activity. The type strain of C. sczc.c.hLrrol\/ticirrn is WM1 ( = . . NRC 2533).A new species belonging to the genus Clostridiurn was isolated during the course of a study of the digestion of cellulose by a highly cellulolytic mixed culture. This culture was obtained from a methanogenic cellulose-enrichment culture started from sewage sludge (4, 5). In the present paper we define the characteristics of and propose a name for this newly discovered microorganism. MATERIALS AND METHODS Media.The basal medium used for the isolation and maintenance of the new isolate was the synthetic saltvitamin medium previously described by Khan et al. (6). The basal medium was supplemented with 0.1% yeast extract and was prepared by the procedure of Holdeman and Moore (1). The pH of the medium was adjusted to 7.2 to 7.4 prior to being reduced by the Hungate technique (2). For the preparation of media containing insoluble substrates, such as cellulose, the reduced medium was dispensed, under 80% N?-20% C 0 2 , in 10-ml volumes into 60-ml serum vials containing preweighed amounts of the substrate and was then autoclaved. Soluble substrates were filter sterilized and were injected by hypodermic syringe into the basal medium after the vials had been autoclaved and cooled. The isolated microorganism was maintained in basal medium supplemented with 2% (wthol) cellobiose and 0.1% yeast extract (YE).Isolation. A methanogenic cellulose-enrichment culture described by Khan (4) was used as the source of inoculum for isolation purposes. The inoculum was heated at 90°C for 15 min and was then serially diluted in basal medium. Prereduced cellobiose-agar slants, inside 160-ml serum vials, supplemented with 0.1% (wthol) YE, were spread with a 0.1-ml quantity of i. Issued as NRCC no. 19895. each dilution. The inoculated agar slants were flushed with an 80% N2-20% C 0 2 gas mixture, sealed, and incubated at 35°C. After 48 h, an individual colony was picked and transferred to cellobiose-YE broth. The broth was heated at 90°C for 15 min, serially diluted, and replated on cellobiose-YE agar. This procedure was repeated a total of five times.Biochemical tests. Biochemical tests were carried out in basal medium containing 0.1% YE and 2% of the selected substrate, by the procedures of Holdeman and Moore (1). The inoculated test vials were incubated at ...

The results of morphological, base ratio, nutritional, temperature, and pH studies on a strain of Methanospirillum hungatii, isolated from an anaerobic pear waste digester, are described. The isolate, designated as strain GP 1, was compared with some of the characteristics of type-strain M. hungatii JF 1. Strain GP 1 is Gram-negative, weakly motile, and a strict anaerobe with a guanine plus cytosine (G +C) content of 46.5 mol%. The preferred substrates for methane production are hydrogen, carbon dioxide, and formate. Acetate is used under certain conditions but its specific contribution to cell carbon and (or) methane formation was not established. The optimum temperature for both growth and methane production is 35 degrees C, but growth and methane production occur over the range 25-45 degrees C. Methane production is optimal at pH 7.0.

A new hybrid reactor, the upflow blanket filter (UBF), which combined on open volume in the bottom two-thirds of the reactor for a sludge blanket and submerged plastic rings (Flexiring, Koch Inc., 235 m(2)/m(3)) in the upper one-third of the reactor volume, was studied. This UBF reactor was operated at 27 degrees C at loading rates varying from 5 to 51 g chemical oxygen demand (COD)/L d with soluble sugar wastewater (2500 mg COD/L). Maximum removal rates of 34 g COD/L d and CH(4) production rates of 7 vol/vol d [standard temperature and pressure (STP)] were obtained. The biomass activity was about 1.2 g COD/g volatile suspended solids per day. Conversion (based on effluent soluble COD) was over 93% with loading rates up to 26 g COD/L d. At higher loading rates conversion decreased rapidly. The packing was very efficient in retaining biomass.