From cheese whey permeate to Sakacin-A/bacterial cellulose nanocrystal conjugates for antimicrobial food packaging applications: a circular economy case study

Manuela Rollini,Cesare Rovera,Alberto Barbiroli,Daniele Bussini,Stefano De Benedetti,Alida Musatti,Daniele Cavicchioli,Stefano Farris,Diego Romano

doi:10.1038/s41598-020-78430-y

Abstract

Applying a circular economy approach, this research explores the use of cheese whey permeate (CWP), by-product of whey ultrafiltration, as cheap substrate for the production of bacterial cellulose (BC) and Sakacin-A, to be used in an antimicrobial packaging material. BC from the acetic acid bacterium Komagataeibacter xylinus was boosted up to 6.77 g/L by supplementing CWP with β-galactosidase. BC was then reduced to nanocrystals (BCNCs, 70% conversion yield), which were then conjugated with Sakacin-A, an anti-Listeria bacteriocin produced by Lactobacillus sakei in a CWP based broth. Active conjugates (75 Activity Units (AU)/mg), an innovative solution for bacteriocin delivery, were then included in a coating mixture applied onto paper sheets at 25 AU/cm2. The obtained antimicrobial food package was found effective in reducing Listeria population in storage trials carried out on a fresh Italian soft cheese (named “stracchino”) intentionally inoculated with Listeria. Production costs of the active material have been mainly found to be associated (90%) to the purification steps. Setting a maximum prudential 50% cost reduction during process up-scaling, conjugates coating formulation would cost around 0.89 €/A4 sheet. Results represent a practical example of a circular economy production procedure by using a food industry by-product to produce antimicrobials for food preservation.

Highlights

Applying a circular economy approach, this research explores the use of cheese whey permeate (CWP), by-product of whey ultrafiltration, as cheap substrate for the production of bacterial cellulose (BC) and Sakacin-A, to be used in an antimicrobial packaging material
In the frame of applying a bio-based circular economy approach, this study aims to explore the use of CWP as cheap substrate for the production of Sakacin-A and bacterial cellulose nanocrystals (BCNCs)
The crystallinity index (CI) of BC was estimated according to the peak height method developed by Segal et al.[40] and calculated to be as high as 82%, in line with the values found by Sacui et al.[41] using a combined CPMAS-NMR/WAXS spectroscopy approach

Summary

Introduction

Applying a circular economy approach, this research explores the use of cheese whey permeate (CWP), by-product of whey ultrafiltration, as cheap substrate for the production of bacterial cellulose (BC) and Sakacin-A, to be used in an antimicrobial packaging material. Bacterial cellulose (BC) is a natural biomaterial industrially produced by acetic acid bacteria belonging to the Komagataeibacter genus (mainly from K. xylinus), through static fermentation of different carbon sources (i.e. glucose, fructose, sucrose, glycerol)[4]. Its industrial production and commercialization at large scale are still hampered by high fermentation costs, low productivity and expensive culture media To address this issue and enhance process sustainability, different studies have focused on using agro and industrial wastes as fermentation feedstock, including cheese whey and its derivatives[8,9]. An interesting potential application of BCNCs involves the use of cellulose nanocomposites to extend the shelf life and enhance the quality of perishable foods, serving as a carrier of active substances (e.g. antimicrobials), in active p ackaging[16]

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