Experimental nisin

Index Entries Nisin whey fermentation optimization experimental design. 

In the present work, the major variables that have significant effects on nisin biosynthesis and lactic acid coproduction from whey were identified, and the optimal conditions for the production of nisin and lactic acid were determined respectively using statistically based experimental designs. In this article, we also discussed the feasibility of simultaneous production of nisin and lactic acid from cheese whey. 

A verification experiment under the conditions of 12 g/L for yeast extract, 0.6 g/L for KH2P04, and 0.6 g/L for MgS04 was conducted separately in order to confirm the optimal conditions obtained from the statistically based experimental designs. After 24 h of fermentation, 92.1 mg/L of nisin and 19.3 g/L of lactic acid were obtained. This result was very close to the predicted value of 92.9 mg/L of nisin and 19.3 g/L of lactic acid. In addition, the nisin result also agreed well with the "ceiling concentration" of nisin previously reported by Kim et al. (23). Therefore, the optimal conditions predicted from the statistically based experimental designs were valid. 

Although this was an essentially static model based on optimized interactions between the peptide and the phospholipids treated as rigid bodies, the results agreed well with experimental data, showing that increasing PG content in the membrane was paralleled with a nisin-induced leakage. 

Bryan G. Reuben is Professor Emeritus of Chemical Technology at London South Bank University. He has written widely on the technology and economics of the chemical and pharmaceutical industries. His most recent experimental work was on hydrogen-deuterium exchange in protonated peptides and on the downstream processing of nisin. 

The presence of two genes, nisB and nisC, encoding 993- and 414-residue proteins without significant homology to other known proteins, but conserved in several lantibiotic operons, has made them strong candidates for post-trans-lational modifications in the maturation pathway of lantibiotics [40]. Limited similarity between NisB and E. coli IlvA, a threonine dehydratase, was reported and hence a dehydratase function for NisB was suggested [40]. Mutation studies of NisB, NisC, EpiB, EpiC, and SpaB indicated that these proteins were essential for nisin, epidermin and subtilin biosynthesis, respectively [40,86,87,190]. As no precursors have been identified and characterized in these mutants, conclusions about the reaction that is catalyzed by these proteins remain speculative [40]. Secondary-structure predictions and experimental evidence confirmed that NisB and SpaB are both membrane-bound [100]. 

Due to the anti-bacterial property of nisin, it was used as safe food preservation in over 50 countries around the world, particularly in dairy products, canned foods, plant protein foods, and cured meat. Investigators from multiple fields have shown promising results for the use of nisin to treat bacterial infections, such as mastitis in humans and cows (Cao et al., 2007 Fernandez et al., 2008 Wu et al., 2007), Staphylococcus aureus infections in atopic dermatitis (Valenta et al., 1996), respiratory tract infections (Bush and Macielag, 2000 De Kwaadsteniet et al., 2009), and experimental gingivitis in dogs (Howell et al., 1993). Since nisin is safe for human consumption as a food preservative, its translation into a clinical setting may be facUltated. 

Hampikyan, H., 2009. Efficacy of nisin against Staphylococcus aureus in experimentally contaminated sucuk, a Turkish-t5fpe fermented sausage. Journal of Food Protection 72,... 

MUcent S, Carrere H. Clarification of lactic acid fermentation broths. Sep Puri Technol 2001 22 393-401. Liu C, Liu Y, Liao W, Wen Z, Chen S. Simultaneous production of nisin and lactic acid from cheese whey optimization of fermentation conditions through statistically based experimental designs. Appl Biochem Biotechnol 2004 114 627-38. 

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