title: Enhancement of nisin production by Lactococcus lactis in periodically re-alkalized cultures.
abstract: Synthesis of nisin as well as biomass production by Lactococcus lactis subsp. lactis CECT (Colección Española de Cultivos Tipo) 539 on both hydrolysed mussel-processing waste and whey medium were followed in three fixed volume fed-batch fermentations, with re-alkalization cycles. The two cultures on mussel-processing waste (MPW) were fed with a 240 g/l concentrated glucose and with a concentrated MPW (about 100 g of glucose/l). The culture on whey was fed with a mixture of concentrated whey (48 g of total sugars/l) and a 400 g/l concentrated lactose. The three cultures were mainly characterized with higher nisin titres [49.7, 109.6 and 124.7 bacteriocin activity units (AU)/ml respectively] compared with the batch process on de Man, Rogosa and Sharpe [(1960) J. Appl. Bacteriol. 23, 130-135] medium (49.6 AU/ml), MPW (9.5 AU/ml) and whey (22.5 AU/ml) [1 AU/ml is the amount of antibacterial compound needed to obtain 50% growth inhibition (LD50) compared with control tubes]. In the three fed-batch cultures a shift from homolactic to mixed-acid fermentation was observed, and other products (acetic acid, butane-2,3-diol or ethanol) in addition to lactic acid were detectable in the medium. However, their contributions to the total antibacterial activity of the post-incubates (the cell-free culture supernatant obtained at the end of the fermentation process) of L. lactis CECT 539 against Carnobacterium piscicola CECT 4020 were very low.
authors.affiliation: Departamento de Bioquímica, Xenética e Inmunoloxía, Facultade de Ciencias de Ourense, Universidade de Vigo, As Lagoas, 32004 Ourense, Spain.
authors.forename: Nelson Pérez
authors.initials: NP
authors.lastname: Guerra
authors.forename: Lorenzo Pastrana
authors.initials: LP
authors.lastname: Castro
mesh_terms: D000818:Animals; D001430:Bacteriocins / Q000494:pharmacology; D001709:Biotechnology / Q000379:methods; D049872:Bivalvia / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D013294:Lactococcus lactis / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D008894:Milk Proteins; D009561:Nisin / Q000096:biosynthesis*; D013997:Time Factors; D000067816:Whey Proteins
chemical_list: D001430:Bacteriocins; D003470:Culture Media; D007220:Industrial Waste; D008894:Milk Proteins; D000067816:Whey Proteins; D009561:Nisin; D005947:Glucose