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D . E R C O L I N I , G . M A U R I E L L O , G . B L A I O T T A , G . M O S C H E T T I A N D S . C O P P O L A . 2003. Aims: To monitor the process and the starter effectiveness recording a series of fingerprints of the microbial diversity occurring at different steps of mozzarella cheese manufacture and to investigate the involvement of the natural starter to the achievement of the final product. Methods and Results: Samples of raw milk, natural whey culture (NWC) used as starter, curd after ripening and final product were collected during a mozzarella cheese manufacture. Total microbial DNA was directly extracted from the dairy samples as well as bulk colonies collected from the plates of appropriate culture media generally used for viable counts of mesophilic and thermophilic lactic acid bacteria (LAB) and used in polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) experiments. The analysis of the DGGE profiles showed a strong influence of the microflora of the NWC on the whole process because after the starter addition, the profile of all the dairy samples was identical to the one shown by the NWC. Simple indexes were calculated for the DGGE profiles to have an objective estimation of biodiversity and of technological importance of specific groups of organisms. LAB grown on Man Rogosa Sharp (MRS) and Rogosa agar at 30� C showed high viable counts and the highest diversity in species indicating their importance in the cheese making, which had not been considered so far. Moreover, the NWC profiles were shown to be the most similar to the curd profile suggesting to be effective in manufacture. Conclusions: The PCR‐DGGE analysis showed that in premium quality manufacture the NWC used as starter had a strong influence on the microflora responsible for process development. Significance and Impact of the Study: The molecular approach appeared to be valid as a tool to control process development, starter effectiveness and product identity as well as to rank cheese quality.

Aims: The identification of a bacteriocin-producing lactococcal strain isolated from raw cow’s milk is reported, along with production conditions, physical and chemical properties, and mode of action of the bacteriocin. Methods and Results: On the basis of resistance to clindamycin, species-specific PCR and amplification of the 16S-23S rDNA spacer region, the strain was identified as Lactococcus garvieae. Its bacteriocin, designated garviecin L1-5, was bactericidal against closely related species and strains of species from different genera, including Listeria monocytogenes and Clostridium spp. Garviecin L1-5 was shown to be proteinaceous by protease inactivation and was unaffected by heat treatments, also at low pH values. When amplifying known lactococcal bacteriocin genes using DNA from strain L1-5 as template, no amplification products were observed on the agarose gel. The molecular weight of garviecin L1-5 was about 2·5 kDa. As far as is known, no bacteriocins have been detected from Lactococcus garvieae. Conclusions: The general properties of garviecin L1-5 are characteristic of the low-molecular-weight bactericidal peptide group. Significance and Impact of the Study: The survey of micro-organisms for novel antimicrobial substances provided valuable information on their physiology, ecology and practical application.