Low-cost purification of nisin from milk whey to a highly active product

food and bioproducts processing 9 3 ( 2 0 1 5 ) 115–121
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Short communication
Low-cost purification of nisin from milk whey to a
highly active product
Angela Faustino Jozala a,∗ , Letícia Celia de Lencastre Novaes a ,
Priscila Gava Mazzola b , Laura Oliveira-Nascimento a ,
Thereza Christina Vessoni Penna a , José António Teixeira c ,
Luis António Passarinha d , João António Queiroz d ,
Adalberto Pessoa Júnior a
Department of Biochemical and Pharmaceutical Technology, School of Pharmaceutical Sciences, Universidade de
São Paulo (USP), São Paulo, Brazil
b Department of Clinical Pathology, School of Medical Sciences, Universidade de Campinas (Unicamp), Brazil
c Department of Biological Engineering, Universidade do Minho, Braga, Portugal
d CICS – Centro de Investigac¸ão em Ciências da Saúde, Universidade da Beira Interior, Covilhã, Portugal
a b s t r a c t
Nisin is a natural peptide used as a preservative in a variety of food products, in which it inhibits mainly Grampositive bacterial growth, including multidrug-resistant pathogens. However, its application range depends on the
cost-effective production and purification of this molecule. Our group has previously produced nisin by Lactococcus
lactis cultivation in milk whey, which is an industrial residue from dairy production. To our knowledge, no report used
milk whey as a culture medium, although several investigators have purified nisin using different techniques. We
thus aimed to establish a low-cost purification of nisin obtained by this process. Samples were diluted in ammonium
sulphate, applied onto HIC columns (butyl sepharose CL 4B matrix), and eluted with Milli-Q water or PBS. Elution
fractions were monitored for protein content and nisin antibacterial activity. Water elution resulted in purification
factor values (270, commercial nisin; 775, nisin produced in-house) higher than those obtained with PBS elution.
We concluded that purification of nisin does not require precipitation with ammonium sulphate, therefore allowing
step/cost reduction. Moreover, purification from milk whey using HIC provides nisin with high activity and low salt
content, which can further be applied to a variety of areas.
© 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Keywords: Nisin; Hydrophobic interaction chromatography (HIC); Milk whey; Purification; Lactococcus lactis; Antimicrobial activity
Certain Lactococcus lactis strains produce the antimicrobial
peptide nisin as a response to the presence of competitive bacteria, including their spores (Delves-Broughton
et al., 1996). Nisin has structure variants due to point
mutation that changes its 34 amino acid chain (Field
et al., 2008). Regardless of the variant, it can conserve
biological products by preventing contamination without
toxicity. This property has guaranteed its use in food
industry as an established preservative (De Arauz et al.,
Corresponding author at: Departamento de Tecnologia Bioquímico-Farmacêutica, Faculdade de Ciências Farmacêuticas da USP, Av. Prof.
Lineu Prestes, 580, B16, 05508-000 São Paulo, SP, Brazil. Tel.: +55 11 3091 2376; fax: +55 11 3815 6386.
E-mail address: [email protected] (A.F. Jozala).
Received 27 February 2013; Received in revised form 4 November 2013; Accepted 7 December 2013
Available online 15 December 2013
0960-3085/$ – see front matter © 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
food and bioproducts processing 9 3 ( 2 0 1 5 ) 115–121
Nisin advantages reached both experimental and commercial frontlines of pharmaceutical, veterinary, and health-care
products (De Arauz et al., 2009; Delves-Broughton et al., 1996;
Liu et al., 2004; Ukuku and Fett, 2004; Sakamoto et al., 2001;
Turner et al., 2004; Aranha et al., 2004; Von Staszewski and
Jagus, 2008). The extent of applications requires different
levels of product purity, which are achieved by several methods including ion exchange, immunoaffinity chromatography,
capillary electrophoresis, ammonium sulfate precipitation,
and liquid-liquid and organic solvent extraction (Cheigh et al.,
2004; Prioult et al., 2000; Suarez et al., 1997; Yang et al., 1992;
Taylor et al., 2007; Jozala et al., 2008; Abts et al., 2011; Espitia
et al., 2012).
Hydrophobic interaction chromatography (HIC) is another
widespread technique for purification of biomolecules, including nisin (Mahn et al., 2005; Passarinha et al., 2007; Josic et al.,
2012). The advantage of HIC for protein purification comes
from its ability to separate closely related variants (Zolodz
et al., 2010). In addition, columns can be packed with a variety of wide range of media by varying the base matrices and
the chemical nature of the ligands, which allows variation
in hydrophobicity and consequent protein selectivity (Perkins
et al., 1997).
Our research group developed an efficient protocol to produce nisin from L. lactis, with whey milk as culture medium
(Jozala et al., 2007). This by-product from dairy industry is
a low-cost alternative for industrial production, which can
provide high yields of this antimicrobial agent. To our knowledge, there are no reports on nisin purification from this
medium. In fact, all methods described for nisin purification used complex formulated media, mostly Man, Rogosa,
and Sharpe (MRS) medium. The aim of the present work
was to purify produced nisin through hydrophobic interaction chromatography (HIC), based on purification profiles of
commercial nisin.
Materials and methods
Bacterial strains and media
L. lactis (ATCC 11454) and Lactobacillus sakei (ATCC 15521)
strains were stored in MRS broth (Difco, Detroit, MI, USA), and
supplemented with 40% glycerol at −80 ◦ C (Jozala et al. 2007).
L. sakei, the nisin-sensitive strain, was grown in MRS broth
or agar (Difco, Detroit, MI, USA). L. lactis, the nisin-producing
strain, was cultivated in milk whey (pH 6.8, kindly provided by
a local dairy plant, Brazil).
Standard nisin
Commercial nisin (2.5%, with sodium chloride and denatured
milk solids, Sigma) was used as a standard during purification.
Nisin production
Initially, a frozen aliquot of L. lactis (108 CFU) was incubated
in MRS broth (50 mL; shaker, 100 rpm, 36 h, 30 ◦ C). An aliquot
(5 mL) from this pre-culture was transferred to milk whey
(50 mL) and incubated (shaker, 100 rpm, 36 h, 30 ◦ C). This culture was sub-cultivated five times, always inoculating aliquots
(5 mL) from the previous culture in fresh milk whey (50 mL),
and incubated in the same conditions (100 rpm, 36 h, 30 ◦ C).
The process was monitored for microorganism contamination
(colony morphology and Gram staining) and nisin activity. The
last sub-culture was centrifuged (13,200 × g, 10 min, and 10 ◦ C),
and the supernatant collected and sterile filtered (22-␮m pore
diameter, Millipore). The sterile solution was called “nisin produced in-house” and stored (4 ◦ C) for further purification.
Agar diffusion assay for determination of nisin
Nisin activity was determined by agar diffusion assay, using
L. sakei as nisin-sensitive microorganism. Serial dilutions of
commercial nisin were utilized to construct the standard
curve (10–105 Arbitrary Units (AU/mL)), as previously described
elsewhere (Arauz et al., 2011). Briefly, L. sakei was grown
in MRS broth (shaker, 100 rpm, 30 ◦ C, 24 h); an aliquot from
this culture was diluted in MRS agar and plated in Petri
dishes (106 UFC/dish). After agar solidification, 3-mm wells
were caved. Samples and standard were independently transferred to wells (50 ␮L/well) and incubated (4 ◦ C, 12 h; 30 ◦ C,
24 h). After incubation, diameter of growth inhibition zones
was determined as the average of four independent measurements. Diameters (mm) determined for commercial nisin
were related to the standard curve (AU/mL) (Fig. 1).
Protein quantification
After elution, the samples were spectrophotometrically monitored (280 nm, Molecular Devices, LLC, USA) for protein
content. Samples with nisin activity were quantified by the
bicinchoninic acid assay (QuantiProTM BCA Assay Kit, Sigma)
according to the manufacturer’s protocol.
Purification of nisin by hydrophobic interaction
Commercial nisin was previously diluted in phosphatebuffered saline (0.1 M, pH 7.2, PBS) or Milli-Q water (100 mg/mL,
4 log10 AU/mL), whereas nisin produced in-house (4982 ␮g/mL
of total protein; 4 log10 AU/mL) was not diluted. To guarantee the hydrophobic interaction, ammonium sulphate was
added to the samples in sufficient amount to achieve 2 M of
final concentration. From these solutions, a sample (3 mL) was
loaded onto the column. A column (10-mm diameter, 10-cm
length) was packed with butyl sepharose CL 4B matrix (5 mL;
GE Healthcare, Uppsala, Sweden). It was equilibrated using
3–4 column volumes (1 mL/min) of ammonium sulphate (2 M)
in PBS (first profile) or water (second profile). Diluted samples were sequentially eluted with 3 column volumes of (a)
2 M ammonium sulphate, (b) 1 M ammonium sulphate and (c)
solvent (PBS or water).
Elution was performed at a 1 mL/min flow rate and each
collected fraction contained 1 mL. Fractions were monitored
by absorbance (280 nm), protein content, and nisin activity.
Eluted samples that exhibited nisin activity were analyzed by
SDS-PAGE (gradient precast gel 4–20%, Bio-Rad, USA) and compared with non-purified commercial nisin. The gel was stained
using the silver stain kit (Bio-Rad, USA). Kaleidoscope polypeptide standard (Bio-Rad, USA) was used as molecular weight
food and bioproducts processing 9 3 ( 2 0 1 5 ) 115–121
Results and discussion
Nisin production/analysis
We produced nisin from sweet whey, as described above,
and labeled it as “nisin produced in-house”. As expected,
no cross-contamination was detected. Nisin produced inhouse (4982 ␮g/mL total protein; 4 log10 AU/mL) was mixed
with ammonium sulphate (1 or 2 M) and tested for antimicrobial activity and protein content after 24 h. Addition of
ammonium sulphate did not change the parameters evaluated over time (p < 0.05, T-test).
Nisin activity is generally measured by the method used
in this paper, while protein content determination of peptides
varied greatly. Protein content was first measured using the
Bradford method, but we did not obtain reproducible results
when testing samples with low protein/high nisin content
(data not shown). The variability might be due to nisin size
(3.4 kDa), which is close to Bradford lower limit (3 kDa), or/and
nisin amino acid sequence, which has only five basic groups
to react with the dye. On the contrary, BCA has an expanded
lower limit (2 kDa) and reacts with peptide bonds at higher
temperatures. Use of BCA in our experiments improved nisin
detection and allowed reproducible results.
Fig. 1 – Agar diffusion assay of the nisin samples. (A)
Commercial nisin activity purified fraction and (B)
commercial nisin activity in crude. The diameter of growth
inhibition zones was determined as the average of four
independent measurements
Statistical and mathematical analysis
Standard curves (log AU × halo diameter) were analyzed by linear regression analysis (R2 > 0.9). Experimental AU values were
calculated using the following equation:
AU/mL = 10[(0.1423×halo diameter)+0.1035]
Yield (Y) and purification factor (PF) were calculated using
the following equations:
PF =
AUfinal /mg total proteinfinal
AUinitial /mg total proteininitial
Y = 100 ×
AUfinal × Vfinal
AUinitial × Vinitial
Nisin elution profiles
Commercial nisin was diluted in water and loaded onto a HIC
column (Fig. 2A). In the first step, the eluate (2 M ammonium
sulphate) contained the highest protein content, although
without nisin activity. In the following step, the eluate (1 M
ammonium sulphate) contained a low amount of protein.
Nisin activity was detected only in the water elution step
(Fig. 2A, samples 35–40), in which protein content was lower
than in the previous steps. Although elution of commercial
nisin with PBS showed a similar profile (Fig. 2B), a decrease was
observed in the number of samples with detectable activity
(Fig. 2B, samples 36–39).
Regardless of the eluent (PBS or water), nisin was selectively eluted in the step without ammonium sulphate. The
second step (elution with 1 M (NH4 )2 SO4 ) of commercial nisin
purification yielded low protein content without nisin activity. Therefore, we decided to suppress this step and perform a
2-step protocol to purify the nisin produced in-house (elution
with 2 M (NH4 )2 SO4 and water or PBS).
Elution of nisin produced in-house exhibited the same
behavior observed with the commercial one; nisin was selectively eluted in the step without ammonium sulphate. A peak
with high protein content was recovered in the first step (2 M
ammonium sulphate, with water or PBS), but no nisin activity was found. Most samples collected in the last step were
highly active (Fig. 3A and B), and some of them even showed
increased activity around 1 log after purification.
Nisin was previously purified (produced in MRS) by HIC, in
which it was also recovered in an eluent without ammonium
sulphate (Gujarathi et al., 2008). However, conditions used in
this work are different from the published literature.
Purification factor and yield
Nisin produced in-house showed the highest values for purification factor (PF) 774 for water elution and 384 for PBS elution,
food and bioproducts processing 9 3 ( 2 0 1 5 ) 115–121
Fig. 2 – Chromatograms of commercial nisin purification by HIC. Black line represents the chromatogram profile recorded at
280 nm (non-bound and bound proteins). Gray solid bars represent nisin activity (Log AU). (A) Commercial nisin, water
elution. (2) Commercial nisin, PBS elution.
3 times higher than PF from commercial nisin it was 268 for
water elution and 135 for PBS elution (Table 1).
Differences between nisin formulations might explain
the discrepancy between yield values for the commercial
and in-house samples: the commercial one contains sodium
chloride, whereas nisin produced in-house was not supplemented with salt. Sodium chloride contributes to lipid
oxidation (Ladikos and Lougovois, 1990) and might increase
Table 1 – Specific activity, yield and purification factor of nisin after HIC purification.
Nisin activity (AU/mL)
Commercial nisin
Water elution
PBS elution
Protein content (␮g/mL)
Specific activity (AU/mg)
Yield (%)
Purification factor (PF)
10, 000
Nisin produced in-house
Water elution
PBS elution
Samples were analyzed before (initial) and after purification with water or PBS as the eluent.
food and bioproducts processing 9 3 ( 2 0 1 5 ) 115–121
Fig. 3 – Chromatograms of nisin produced in-house purification by HIC. Black line represents the chromatogram profile
recorded at 280 nm (non-bound and bound proteins). Gray solid bars represent nisin activity (Log AU). (A) Nisin produced
in-house, water elution. (B) Nisin produced in-house, PBS elution.
nisin availability, since nisin-fat clusters were reported to
reduce antimicrobial activity (Jung et al., 1992). In addition,
this salt prevents formation of insoluble protein aggregates
(Costantino et al., 1995; Middelberg, 2002) that may entrap
active nisin. Despite sodium chloride advantages in this
case, it is likely that the salt interferes with nisin sporicidal
activity (Bell and Lacy, 1985) and may reduce HIC efficiency
(Roettger et al., 1989). High salt concentration can also induce
hyperosmotic stress and kill cells (Burg et al., 2007), which is
an undesired outcome for in vitro cytotoxicity tests.
We believe that HIC purification concentrated the active
peptide in commercial samples, resulting in high values for
PF. A selection to obtain the most purified fractions can significantly reduce their yield (Ward and Swiatek, 2009), as occurred
in this purification. On the contrary, nisin produced in-house
has demonstrated better activity than commercial nisin. In
this case, purification probably separated impurities that were
interacting with nisin in the crude extract. The increase in
activity resulted in high values for PF and yield.
Regarding the eluent effect, the values for yield and PF
in all preparations eluted with water were higher than those
eluted with PBS (Table 1). This might be explained by the pH
factor: nisin is more active in acidic solutions, whereas PBS
maintains a neutral pH. As a consequence, the antimicrobial
activity decreases, which reflects on the yield/PF values.
Fig. 4 – SDS-PAGE (gradient gel 4–20%, silver stain).
SDS-PAGE (gradient precast gel 4–20%, Bio-Rad, USA). The
gel was stained using the silver stain kit (Bio-Rad, USA).
Kaleidoscope polypeptide standard (Bio-Rad, USA) was
used as molecular weight standard. At 150 V, 200 mA for
90 min. (A) Molecular weight standard; (B) purified form of
commercial nisin; (C) purified fraction of nisin produced
in-house; (D) commercial nisin in crude.
food and bioproducts processing 9 3 ( 2 0 1 5 ) 115–121
Researchers Gujarathi et al. (2008), who purified MRSderived nisin using HIC, obtained 50% recovery and a PF of
10.87. As stated above, most conditions used by this group
were different from ours: their protocol involved several purification steps; the sample was previously concentrated by
ammonium sulphate precipitation; the column was packed
with phenyl Sepharose instead of butyl Sepharose, among
other details (Gujarathi et al., 2008). To our knowledge, there
are no articles describing purification of whey milk-derived
nisin, thus precluding any comparisons.
Purified and crude samples were subjected to SDS-PAGE
(4–20%) and revealed with silver (Fig. 4). The gels showed the
“smiley effect”, probably due to high salt content in some
samples. Purified samples showed no bands but nisin, in
agreement with nisin activity (high) and protein content (low)
assays. As expected, commercial nisin (not purified, Fig. 3B)
showed multiple bands and contained high protein content.
The present study established a low-cost purification of milk
whey-derived nisin by HIC. We obtained a high degree purification of nisin without protein precipitation, which allows
step/cost reduction. It was possible to recover nisin with water
or PBS, which allows more possible applications of nisin.
Water was the best eluent, with an increase of up to 775fold in the antimicrobial activity. As per the outcomes of this
work, milk whey probably contains factors, as remains of
precipitated proteins, derived from the nisin production process, that decrease its activity, although high activity values
were obtained in the crude extract. These factors were easily removed by HIC purification, evidenced by an even higher
antimicrobial activity.
We conclude that production of nisin using milk whey as
culture medium and HIC in the downstream process is costeffective and results in a highly purified nisin product.
This study was supported by grants from CAPES (Coordenac¸ão
de Aperfeic¸oamento de Pessoal de Nível Superior, Brazil), CNPq
(Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brazil) and FAPESP (Fundac¸ão de Amparo à Pesquisa
do Estado de São Paulo, Brazil). We thank Dr. Paulo Boschcov
for his careful and critical reading of our final manuscript.
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