Micrococcus freudenreichii

Micrococci comprise approximately 78% of the nonlactic bacteria in raw milk Cheddar cheese (Alford and Frazier 1950). The proteolytic system of Micrococcus freudenreichii functions optimally at 30 °C and at a pH near neutrality (Baribo and Foster 1952). An analysis of pro-teinases present in 1-year-old Cheddar cheese indicates that micrococci may contribute to proteolytic activity (Marth 1963). Proteolytic micrococci also contribute to the ripening of surface-ripened cheeses such as brick and Camembert (Lenoir 1963 Langhus et al. 1945). Micrococcal proteases probably contribute to development of ripened cheese flavor when ripening temperatures are above 10°C (Moreno and Kosikowski 1973). This effect results from degradation of /3-casein. 

Lawrence et al. (1967) reported some preference for long-chain triglycerides by a P. fragi lipase but for short-chain triglycerides by a lipase from Micrococcus freudenreichii. Temperature may have an influence on the apparent specificity of lipolysis, with relatively more short-chain and unsaturated fatty acids being released from milk fat at lower temperatures. This appears to be a reflection of the physical state of the substrate (Alford and Pierce, 1961 Sugiura and Isobe, 1975). 

Alternatively, a one-pot, single-step deracemization of sec-alcohols has been achieved by employing two different microorganisms in a single reaction vessel. However, the number of examples of this type is limited and the oxidation and reduction steps are usually performed sequentially in a one-pot, two-step procedure. For instance, racemic mandeUc acid was deracemized in the presence of whole cells of Pseudomonas polycdor and Micrococcus freudenreichii [14]. Separate experiments showed that P. polycolor was responsible for the oxidation, while M. freudenreichii was needed for reduction of the corresponding a-keto acid. After 24h, (R)-mandelic acid 4 was isolated in a 60% yield and 99% e.e. [14],... 

Alford et al. [94] have reported on the action of various nticroorganisms on lard oxidation. They found 10 of the 28 nuCToorganisms studied destroyed the low levels of peroxide in fresh lard. Fourteen of the 28 had no effect on peroxides in the lard, while five strains of streptomyces increased peroxides by threefold. Pseudomonas ovalis increased peroxides by 8-fold, and Micrococcus freudenreichii increased peroxides 14-fold. The extent of oxidation observed in the lard was found to be very dependent upon the microtlora present in the lard. 

Other nonstarter bacteria (e.g.. Micrococcus and Pediococcus) also produce lipases. It is generally believed that lipases from Micrococcus spp., when present in cheese, can contribute to lipolysis during ripening (Bhow-mik and Marth, 1990b). The lipase of M. freudenreichii was strongly inhibited by organophosphates and divalent metal ions, but less so by EDTA or pCMB (Lawrence et al., 1967). 

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