Bacteriophages specific for Pediococcus halophilus, a group of halophilic lactic cocci used as starters for soy sauce fermentation, were isolated from fermenting soy sauce moromi-mash. Typical two of these phages, q57116 and qD-86, which propagate on P. halophilus NISL 7116 and D-86 respectively, were purified and studied for their morphology and some infecting properties. Morphotype of q57116 was Ackermann's Al having an isometric head of 87-96 nmi diameter and a contractile tail of 200 nm length. q5D-86 was found to be morphotype B 1, having a 67 nm isometric head and a 300 nm noncontractile tail. Both the phages could propagate on their each host under any pH or salt conditions in which their hosts could grow. Latent periods were both 5 h and burst sizes were 27-28. Their host ranges were substantially strain-specific. They both thermally inactivated at 60°C. Stable pH ranges for X7116 and qD-86 were 5.0-8.8 and 4.4-10.7 respectively.In diluted NaCI solutions, qD-86 was fairly stable over 0.03-2.6 M but q57116 was unstable specifically between 0.04-0.1 M.In an earlier stage of the soy sauce moromi-fermentation, a group of halophilic lactic cocci, Pediococcus halophilus, propagates, usually up to 108 cfu/ml level, in moromi-mash which contains nearly 3 M (18% [w/v]) of sodium chloride (16). They make a significant contribution to the quality of soy sauce through lactic acid fermentation and other metabolic activities. There has been recently a trend to control the fermentation by inoculating moromi-mash with artificial cultures of this species.A variety of bacteriophages infecting lactic-acid bacteria have been known.

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Several strains of non-citrate-metabolizing Pediococcus halophilus have previously been isolated from soy sauce mash or moromi. The factors controlling the metabolism of citrate in soy pediococci were studied. All the soy pediococcal strains tested which failed to decompose citrate did not possess citrate lyase [citrate (pro-3S)-lyase; EC 4.1.3.6] activity. In P. halophilus, citrate lyase was an inducible enzyme, and the optimum pH for activity was 7.0. The metabolism of citrate in P. halophilus was different from that observed in lactic streptococci. The main products from citrate were acetate and formate, and this bacterium produced no acetoin or diacetyl. Formate production from citrate was greatly reduced in the presence of glucose. P. halophilus 7117 (Cit+) was proved to contain citrate lyase, pyruvate formate-lyase (EC 2.3.1.54) phosphotransacetylase (phosphate acetyltransferase; EC 2.3.1.8), and acetate kinase (EC 2.7.2.1), i.e., all the enzymes necessary to convert citrate to acetate and formate.

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