Disclosed is an isolated Lactococcus lactis subsp. lactis selected from the group: MCC852 bacterium deposited at the International Patent Organism Depositary (IPOD) on 1 December 2006 and designated accession no. FERM BP-10742; MCC857 bacterium deposited at IPOD on 10 January 2007 and designated accession no. FERM BP-10757; MCC859 bacterium deposited at IPOD on 1 December 2006 and designated accession no. FERM BP-10744; MCC865 bacterium deposited at IPOD on 1 December 2006 and designated accession no. FERM BP-10745; or MCC866 bacterium deposited at IPOD on 1 December 2006 and designated accession no. FERM BP-10746.