Proteins with molecular mass ranging from 165 kDa (size of DsrD, the Leuconostoc mesenteroides dextransucrase, [28] ) to 9.8 kDa (size of Afp1, a Streptomyces tendae antifungal protein; Freitas et al., submitted) have been successfully secreted in L. lactis. This suggests that protein size is not a serious bottleneck for heterologous protein secretion in L. lactis. In contrast to protein size, conformation may be a major problem for heterologous secretion in L.