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The search for new food products that promote consumers health has always been of great interest. The dairy industry is perhaps the best example regarding the emergence of new products with claimed health benefits. Cheese whey (CW), the by-product resulting from cheese production, and second cheese whey (SCW), which is the by-product of whey cheese manufacture, have proven to contain potential ingredients for the development of food products with improved nutritional characteristics and other functionalities. Nowadays, due to their nutritional quality, whey products have gained a prominent position among healthy food products. However, for a long time, CW and SCW were usually treated as waste or as animal feed. Due to their high organic content, these by-products can cause serious environmental problems if discarded without appropriate treatment. Small and medium size dairy companies do not have the equipment and structure to process whey and second cheese whey. In these cases, generally, they are used for animal feed or discarded without an appropriate treatment, being the cause of several constraints. There are several studies regarding CW valorization and there is a wide range of whey products in the market. However, in the case of SCW, there remains a lack of studies regarding its nutritional and functional properties, as well as ways to reuse this by-product in order to create economic value and reduce environmental impacts associated to its disposal.

The second cheese whey (SCW) is the liquid fraction that remains after the production of whey-cheeses. SCW appears as a white to yellow/green opalescent liquid with suspended solids and contains up to 6% lactose and variable amounts of proteins, fats, and mineral salts. Due to its organic load, SCW is characterized by levels of Biochemical Oxygen Demand and Chemical Oxygen Demand that are significantly higher than urban wastewater. Therefore, it poses an environmental challenge and represents a significant cost and a problem for cheese production facilities when it comes to disposal. On the flip side, SCW contains valuable nutrients that make it a cost-effective substrate for bio-based productions including lactose extraction, and the production of lactic acid, bioethanol, eco-friendly bioplastics, biofuels, beverages, bioactive peptides, and microbial starters. A search in Scopus database indicates that despite the numerous potential applications, interest in SCW exploitation is surprisingly limited and, accordingly, sustainable management of SCW disposal remains an unresolved issue. In this review, which marks the first exclusive focus on SCW, with the aim of contributing to increase the interest of both the scientific community and the stakeholders in the exploitation of this by-product, the processes aimed at SCW valorisation will be described, with particular attention to its use in the production of beverages, food and feed, single cell proteins and as a source of biodegradable bioplastics, organic acids and renewable energy. Moreover, to provide valuable insights into its applications and innovations, an overview on patents regarding the exploitation of SCW will be presented.

Whey permeate (WP), the main waste stream of the dairy industry, was used as a raw material to produce fully bio-based non-ionic surfactants. Specifically, on the one hand, WP was submitted to a transglycosylation reaction catalyzed by the immobilized β-galactosidase from Aspergillus oryzae in 1-BuOH, affording 1-butyl β-D-galactopyranoside (yield 40%), which was used as the polar “head” of the surfactant. On the other hand, a WP-based fermentation process by the yeast Cutaneotrichosporon oleaginosus ATCC 20509 was employed to produce single cell oil (45% w/w cell dry weight ). The microbial lipids were recovered from the freeze-dried cells and derivatized in a one-pot system by acid-catalysis to yield the corresponding ethyl esters as apolar “tails” (75% w/w yield, based on lipid content). These bio-based building blocks were converted into the sugar fatty acid esters (SFAE) n -butyl 6- O -acyl-β-D-galactopyranosides by a lipase-catalyzed transesterification reaction (yield 40%). The hydrophilic–lipophilic balance and solubility parameters of the synthesized SFAE mixture were calculated. Additionally, its ability to reduce the interfacial tension was examined, including the effect of fatty tail unsaturation. The interfacial performance of the SFAE mixture, containing both palmitic (45%) and oleic (40%) acid residues, was lower (6.3 mN m⁻ 1 ) compared to the SFAE containing only palmitic acid as the fatty acid tail (0.1 mN m⁻ 1 ) at the same concentration, but still highly promising. Key points • Whey permeate (WP) is the main waste stream of dairy industry. • WP was upcycled by coupling fermentation and biocatalysis. • Bio-based surfactants (sugar fatty acid esters) were obtained using WP as biomass. Graphical Abstract

Whey from cheesemaking is an environmental contaminant with a high biochemical oxygen demand (BOD), containing an abundance of lactose. Hence, it has the potential to be utilized in the manufacturing of bio-based chemicals that have increased value. A designed sequential fermentation approach was employed in this research to convert enzymatic hydrolysate of cheese whey (primarily consists of glucose and galactose) into gluconic acid and bio-ethanol. This conversion was achieved by utilizing Gluconobacter oxydans and Saccharomyces cerevisiae . Glucose in the enzyme hydrolysate will undergo preferential oxidation to gluconic acid as a result of the glucose effect from Gluconobacter oxydans . Subsequently, Saccharomyces cerevisiae will utilize the remaining galactose exclusively for ethanol fermentation, while the gluconic acid in the fermentation broth will be retained. As a result, approximately 290 g gluconic acid and 100 g ethanol could be produced from 1 kg of cheese whey powder. Simultaneously, it was feasible to collect a total of 140 g of blended protein, encompassing cheese whey protein and bacterial protein. Two-step fermentation has proven to be an effective method for utilizing cheese whey in a sustainable manner.

Biosurfactants constitute amphiphilic molecules, receiving increased attention as environmentally benign, biodegradable alternatives to substitute for the petroleum derived counterparts in food, pharmaceutical and cosmetics applications. However, their high production cost hinders industrial production. In this study, fifty GRAS lactobacilli strains were screened for their ability to produce biosurfactants, implementing different substrates. Cheese whey permeate (CWP) was also assessed as a low-cost and inherent lactobacilli substrate, aiming to mitigate its polluting impact, expand valorization strategies, alleviate costs deriving from commercial supplements and enhance overall sustainability. Surface tension, emulsification activity (E24) and oil displacement were deployed to identify the most promising candidates. Results reveal surface tension as the most robust method and underline the effect of substrate on biosurfactant synthesis. Likewise, this study indicates the fundamental role of including the final fermentation substrate (CWP) during strain selection to avoid misinterpretation of results and enhance subsequent bioprocess integration.

We report a novel production process for lactobionic acid (LBA) production using an engineered Neurospora crassa strain F5. The wild-type N. crassa strain produces cellobiose dehydrogenase (CDH) and uses lactose as a carbon source. N. crassa strain F5, which was constructed by deleting six out of the seven β-glucosidases in the wild type, showed a much slower lactose utilization rate and produced a much higher level of cellobiose dehydrogenase (CDH) than the wild type. Strain N. crassa F5 produced CDH and laccase simultaneously on the pretreated wheat straw with 3 µM of cycloheximide added as the laccase inducer. The deproteinized cheese whey was added directly to the shake flasks with the fungus present to achieve LBA production. Strain F5 produced about 37 g/L of LBA from 45 g/L of lactose in 27 h since deproteinized cheese whey addition. The yield of LBA from consumed lactose was about 85%, and the LBA productivity achieved was about 1.37 g/L/h.

The milk whey remaining at the end of the cheese-making process is the main by-product of the dairy industries and it is currently used as a source of high added-value compounds by the food and pharmaceutical industries. The aim of this research was to study the effects of the season on the residual whey characteristics in the Parmigiano Reggiano cheese-making process. Over two years, a total of 288 cheese-making trials of Parmigiano Reggiano PDO (Protected Designation of Origin) cheese were performed in three commercial cheese factories and, in each trial, a sample of the vat milk (V-milk) and of the residual whey (C-whey) were collected. The C-whey values of dry matter and non-fat matter were higher in winter and autumn than in spring and summer. Moreover, the C-whey fat and crude protein contents were also higher in autumn (0.52 and 0.89 g/100 g, respectively) and lower in spring (0.44 and 0.83 g/100 g, respectively) and summer (0.46 and 0.84 g/100 g, respectively). Furthermore, crude whey protein resulted to be the major fraction of crude protein (97.96%). Crude whey protein and true whey protein were higher in autumn and lower in spring and summer and their values mainly depended on milk whey protein. Finally, the C-whey average contents of phosphorus and magnesium were higher in autumn and winter than in summer.

The present work describes the utilisation of cheese whey to produce biohydrogen by sequential dark-photo fermentation. In first stage, cheese whey was fermented by Enterobacter aerogenes 2822 cells in a 2 L double-walled cylindrical bioreactor to produce hydrogen/organic acids giving maximum biohydrogen yield and cumulative hydrogen of 2.43 ± 0.12 mol mol−1 lactose and 3270 ± 143.5 mL at cheese whey concentration of 105 mM lactose L−1. The soluble metabolites of dark fermentation when utilised as carbon source for photo fermentation by Rhodobacter sphaeroides O.U.001, the yield, and cumulative hydrogen was increased to 4.22 ± 0.20 mol mol−1 VFA and 3800 ± 170 mL, respectively. Meanwhile, an overall COD removal of about 38.08% was also achieved. The overall biohydrogen yield was increased from 2.43 (dark fermentation) to 6.65 ± 0.25 mol mol−1 lactose. Similarly, the modelling for biohydrogen production in bioreactor was done using modified Gompertz equation and Leudeking-Piret model, which gave adequate simulated fitting with the experimental values. The carbon material balance showed that acetic acid, lactic acid, and CO2 along with microbial biomass were the main by-products of dark fermentation and comprised more than 75% of carbon consumed.

Abstract The batch production of Chlorella vulgaris and its potential to profit the remnant nutritional components from ricotta cheese whey (RCW) were evaluated. From a first screening test, undiluted ricotta cheese whey was selected to be used as a growth media in the subsequent assays. Three different RCW pre-treatment methods were tested and compared: centrifugation, heat treatment (HT) and tangential flow microfiltration (TFMF). Based on the results of the screening test, a macronutrient supplementation assay was performed to increase the biomass production. A central composite design was used to analyse the effect of supplementing the media with nitrogen (0; 3.3 and 6.6 g L−1) and phosphorous (0; 0.27 and 0.55 g L−1). Chlorella vulgaris was able to grow in all tested RCW concentrations. All RCW pre-treatment methods resulted in an enhancement of the growth kinetic parameters (GKP) of Chlorella vulgaris. Among them, TFMF technology presented the best performance. The macronutrient supplementation did not show an enhancement in GKP. The scaled-up production until 400 mL batch using micro-filtered RCW showed a μmax value of 0.41 ± 0.05 h−1 (9.9 ± 1.2 day−1), a lag period of 19.9 ± 0.7 h and a Cmax of 2.52 ± 0.09. A final biomass concentration of 2.28 g L−1 was obtained. In addition, chemical oxygen demand (COD), phosphorus and nitrogen removals of 26 ± 1%, 75 ± 1% and 55 ± 1% were respectively achieved. The use of TFMF and Chlorella vulgaris cultivation represents a sustainable proposal for contributing to the circular economy.

Goat and second cheese whey from sheep’s milk are by-products of the manufacture of goat cheeses and whey cheeses from sheep. Due to their composition which, apart from water—about 92%—includes lactose, proteins, fat, and minerals, and the elevated volumes generated, these by-products constitute one of the main problems facing to cheese producers. Aiming to add value to those by-products, this study evaluates the efficiency of ultrafiltration/diafiltration (UF/DF) for the recovery of protein fraction, the most valuable component. For a daily production of 3500 and using the experimental results obtained in the UF/DF tests, a membrane installation was designed for valorization of protein fraction, which currently have no commercial value. A Cost–Benefit Analysis (CBA) and Sensitivity Analysis (SA) were performed to evaluate the profitability of installing that membrane unit to produce three new innovative products from the liquid whey protein concentrates (LWPC), namely food gels, protein concentrates in powder and whey cheeses with probiotics. It was possible to obtain LWPC of around 80% and 64% of crude protein, from second sheep cheese whey and goat cheese whey, respectively. From a survey of commercial values for the intended applications, the results of CBA and SA show that this system is economically viable in small/medium sized cheese dairies.