Use of poly(N-isopropylacrylamide) nanohydrogels for the controlled release of pimaricin in active packaging.

UNLABELLED: We propose here a delivery drug-polymer system using poly(N-isopropylacrylamide) (PNIPA) nanohydrogels that enables pimaricin to be protected from hostile environments and allows the controlled release of the antifungal through environmental stimuli. We synthesized 2 nanohydrogels, 1 with 100% N-isopropylacrylamide (PNIPA(5)) and 1 with 80% N-isopropylacrylamide copolymerized and 20% acrylic acid (PNIPA-20AA(5)). Both were then, loaded with a pimaricin aqueous solution. The pimaricin release profiles of these 2 nanohydrogels were considerably different: PNIPA(5) released 10% and PNIPA-20AA(5) released 30% with respect to the free pimaricin release. Moreover, the diffusion experiments showed that pimaricin was released from the PNIPA-20AA(5) nanohydrogel for up to 3 times longer than free pimaricin. Therefore, incorporating acrylic acid as comonomer into the PNIPA nanohydrogel resulted in a slower but more continuous release of pimaricin. The highest pimaricin levels were reached when the most hydrophilic nanohydrogel was used. The bioassay results showed that the pimaricin-nanohydrogel system was highly effective in inhibiting the growth of the indicator strain in conditions of thermal abuse. The spoilage in acidified samples stored under fluorescent lighting was reduced by 80.94% ± 33.02% in samples treated with a pimaricin-loaded nanohydrogel, but only by 19.91% ± 6.68% in samples treated with free pimaricin. Therefore, 2 conclusions emerge from this study. One is that the nanohydrogel delivery system could impede the degradation of pimaricin. The other is that the inhibitory effect of the antifungal on yeast growth is more pronounced when it is added included into the nanohydrogel to the food, especially in an acidic environment. PRACTICAL APPLICATION: This article presents relevant results on the use of nanohydrogels in food packaging. Nanohydrogels could provide protection so that the pimaricin remains active for a longer time. They also allow the controlled release of pimaricin, which thus regulates the unnecessary presence of the antifungal in the food.

Development of a bioactive packaging cellophane using Nisaplin as biopreservative agent.

AIMS: Production of a nisin-containing cellophane-based coating to be used in the packaging of chopped meat. METHODS AND RESULTS: The adsorption of nisin to cellophane 'P' type surface was studied at 8, 25, 40 and 60 degrees C using different concentrations of nisin. Then, the antimicrobial activity of adsorbed nisin to cellophane surface was determined in fresh veal meat for effectiveness in reducing the total aerobic bacteria. The adsorption of nisin to cellophane was higher at 8 degrees C. The developed bioactive cellophane reduced significantly the growth of the total aerobic bacteria (by ca 1.5 log units) through 12 days of storage at 4 degrees C. CONCLUSIONS: Bioactive cellophane packaging could be used for controlling the microbial growth in chopped meat. SIGNIFICANCE AND IMPACT OF THE STUDY: Nisin-adsorbed bioactive cellophane would result in an extension of the shelf life of chopped meat under refrigeration temperatures.

Influence of pH drop on both nisin and pediocin production by Lactococcus lactis and Pediococcus acidilactici.

AIMS: To develop a kinetic model for describing the specific effect of pH drop on nisin and pediocin production in whey. METHODS AND RESULTS: The effect of pH drop on both bacteriocin productions was tested in non-buffered whey and whey buffered at initial pH 6.3 with 0.03, 0.10 and 0.25 mol l-1 of potassium hydrogen phthalate-NaOH. An accurate description of the experimental data of nisin and pediocin obtained at different pH drops is obtained with the proposed model. CONCLUSIONS: The proposed model was able to typify both bacteriocins as pH-dependent primary metabolites. SIGNIFICANCE AND IMPACT OF THE STUDY: The decisive role of pH drop for bacteriocin production on whey was demonstrated and modelled. This study contributes to a better understanding of underlying metabolic regulatory mechanisms, which could facilitate the optimization of bacteriocin production for upscaling.

Nisin and pediocin production on mussel-processing waste supplemented with glucose and five nitrogen sources.

AIMS: Optimization of bacteriocin production by L. lactis subsp. lactis CECT 539 and Ped. acidilactici NRRL B-5627 on mussel-processing wastes. METHODS AND RESULTS: The concentrations of glucose and five nitrogen sources that optimize nisin and pediocin production were determined using a second order orthogonal factorial design. NH4Cl, glycine and glutamic acid were poor nitrogen sources. Enhanced pediocin and nisin productions were achieved in a medium supplemented with yeast extract or Bacto casitone. CONCLUSIONS: Mussel-processing wastes could be successfully used as a culture medium for bacteriocin production at low production cost. SIGNIFICANCE AND IMPACT OF THE STUDY: Average optimization led to a threefold increase in pediocin production (from 322 to 934 BU ml(-1)) and in nisin production (from 32 to 100 BU ml(-1)) when compared with the unsupplemented medium. For this reason, mussel-processing waste warrants further investigation due to its potential use as a cheap culture medium for upscaling bacteriocin production.

Nutritional factors affecting the production of two bacteriocins from lactic acid bacteria on whey.

The ability of Lactococcus lactis subsp. lactis CECT 539 and Pediococcus acidilactici NRRL B-5627 to produce bacteriocins on both diluted and concentrated whey was investigated in batch fermentations. Both strains produced the higher amounts of biomass and bacteriocin titres on diluted whey. Luedeking and Piret expression was able to model the production of nisin, which was produced as a primary metabolite on both culture media. However, the pediocin production could not be typified in any case due to the negligible growth of P. acidilactici. Although the whey supported the growth and bacteriocin production by the two strains, both biomass and bacteriocin productions were lower than those obtained on MRS broth. The effect of total sugar, nitrogen, phosphorous and buffer concentrations on the production of nisin and pediocin was studied in diluted whey using factorial experiments and empirical modelling. The production of nisin was greatly inhibited by the increase in nitrogen, buffer, and to a lesser extent, sugar concentration in the medium, nevertheless, the used phosphorous source produced a light stimulatory effect on bacteriocin synthesis. In addition, the growth of Lc 1.04 was mainly affected by the nitrogen source used. On the other hand, pediocin was inhibited by the increase in buffer, phosphorous, and to a lesser degree, by the sugar and nitrogen concentration. The inhibitory activity of pediocin disappeared almost totally after 15 min of treatment with trypsin, papain, subtilisin and pepsin. The activity of nisin was drastically reduced by treatment with trypsin, subtilisin and pepsin. Nevertheless, 50% of the initial activity was retained when nisin was treated with papain. Both bacteriocins showed the highest heat stability at acidic pH and short incubation times.