La Prensa MedicaISSN: 0032-745X

Research Article, Prensa Med Argent Vol: 103 Issue: 4

Milk Whey- From a Problematic Byproduct to a Source of Valuable Products for Health and Industry: An Overview from Biotechnology

Chanfrau JMP1, Pérez JN1, Fiallos MVL1, Leonor Rivera2,3, Abril VH4, Guerrero MJC1 and Toledo LET4*

1Department of Engineering in Agricultural and Environmental Sciences, Technical University of the North, Eucador

2Technical University of Machala, Machala, El Oro, Ecuador

3Postgraduate Unit of the National University of San Marcos-Peru

4Industrial Biotechnology and Bio products Research Group, Center for Nanoscience and Nanotecnology, CENCINAT, University of the Armed Forces (ESPE), Ecuador

*Corresponding Author : Luis E Trujillo Toledo
Industrial Biotechnology and Bio products Research Group, Center for Nanoscience and Nanotecnology, CENCINAT
Universidad de las Fuerzas Armadas (ESPE), Ave. Rumiñahui s/n. Quito, Pichincha, Ecuador
E-mail: [email protected]

Received: August 01, 2017 Accepted: August 12, 2017 Published: August 17, 2017

Citation: Chanfrau JMP, Pérez JN, Fiallos MVL, Rivera L, Abril VH, et al. (2017) Milk Whey- From a Problematic Byproduct to a Source of Valuable Products for Health and Industry: An Overview from Biotechnology. Prensa Med Argent 103:4. doi: 10.4172/lpma.1000254

Abstract

Esmeraldas, Carchi, Ibarra and Sucumbíos are Ecuadorian provinces that produce daily more than 407 m3 of milk. Almost a third of all this production is used to produce different types of cheeses, generating near to 122 m3 of whey in the provinces of Carchi and Imbabura. An important part of whey is used in animal feed, but unfortunately, a vast amount is poured into rivers, streams, etc.; polluting natural sources of water. More stringent environmental regulations joined to producers’ awareness, highlights the need to transform whey into less polluting effluents. If, as a result of this transformation, it is possible to obtain a range of new products with higher added value than the whey itself, the resources used in the conversion would be partially amortized. In the present review, some of the available technologies are explored from the biotechnology point of view to overcome this problem in the context of Zone 1 of Ecuador.

Keywords: Milk whey; Whey permeate; Single-cell protein; Lactic acid; Kefiran; Galactooligosaccharides

Introduction

Carchi, Imbabura, Esmeraldas and Sucumbíos, are Ecuadorian provinces in which agricultural and livestock activities constitute a significant part of the economy and jobs source of these territories. The majority of the population in these zones is dedicated to the production and commercialization of milk, being the Carchi province the most outstanding productive region, reaching 4.8% of the national milk production. A daily delivery of Ecuador is around 79.8 m3 with a production value of about US $ 3.5 million per year [1].

After whole milk, the most consumed dairy products in Ecuador are fresh cheeses like creole, mozzarella, kneading and curds [2]. In eight years (2006-2014) the per capita consumption of cheese in Ecuador was doubled, from 0.75 kg per person per year in 2006 to 1.57 kg in 2014 [2]. Sales of the cheese industry increased 3.4 times between 2006 and 2016, from US$ 71.4 million to US$ 243.1 million [2].

About one-third of dairy production in the region is devoted to the cheese manufacture [2]. As a result of the production of different types of cheeses, milk whey (sweet (SW) or acid (AW) whey) is obtained. For every 100 kg of milk used to produce cheeses, 9.3 ± 0.7 kg of fresh cheese [3] and around 90.7 kg of SW/AW [4,5] are obtained. The SW/AW retains a large part of the nutrients contained in the milk so; biotechnology has proposed some possible ways to use this by-product [4,6-9] useful as animal food [10-12] and in biological treatment with sludge to produce organic fertilizers for soil improvement [13,14].

In this sense, due to its high lactose levels, the SW/AW is a significant pollutant with values of 30-50 kg m-3 of biological oxygen demand (BOD5) [15], and its dumping to lakes, rivers, and soils should be avoided.

One of the most attractive uses of SW/AW is the development of products based on whey proteins [6,16-19], providing a protein concentrate of excellent quality for human and animal consumption [16]. However, as a result of the whey protein isolation process, a whey permeates (PW) of milk with a high lactose content is obtained, and therefore with high pollutant load values [20,21]. Various uses have been proposed for PW, ranging from the production of unicellular microbial protein for animal feed [10,12], the production of organic acids [22,23], alcohols [24,25], also the production of probiotics [9] and different prebiotic substances [26-28].

The objective of this review is to explore various technical solutions from the biotechnology point of view that contributes to the use and valorization of SW/AW or PW encouraging the continued growth of the Dairy Industry in Ecuador.

Milk whey

A byproduct of cheese production, the main constraint to the growth of the dairy sector

According to Association of Livestock of the Sierra and East of Ecuador (AGSO), in 2017 an average of 5.4 million liters of milk was registered daily at the national level [29]. In the “Sierra” region, milk production reaches 77% of the total, whereas Imbabura and Carchi produce 7.4% of the national milk production, which represents more than 407 m3 of whole milk per day. From those, near of 135.7 m3 is destined to cheese production, and near of 122 m3 of milk whey daily is generated in Carchi and Imbabura provinces.

Milk whey (SW/AW) represents 85-95% of the volume of milk and retains 55% of all the nutrients contained in milk [30,31]. SW/ AW represents the main by-product and the highest contaminant in dairy production [15,32,33], reaching values of chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) of 60-80 and 30-50 kg m-3, respectively [34,35].

Globally, around 180-190 million metric tons (TM) of whey were produced in 2013 [36,37]. For this, 40% of this production is used in direct feed, as fertilizer, or discarded, while the rest is industrially transformed basically in the production of whey powder, lactose and whey protein concentrates as shown in Figure 1.

Figure 1: Global production of whey (2013) and its uses.

As Kosikowski rightly points out, “dispose of” is not the same thing that to “use” the milk whey [5]. Even today, significant amounts of SW/AW are discharged into rivers and streams or are sprayed directly into cultivated fields after dilution. The latter, in spite of the apparent advantages that could be observed, after long periods of shedding, the high salt content in the SW/AW tends to salinize the soils, thus diminishing agricultural yields.

Also, increasing awareness of these adverse effects is becoming increasingly prevalent, and states’ environmental laws and regulations tend to prohibit such practices. As a consequence, small and medium-sized cheese producers could find it difficult to compete in the market with large companies, given the need to have adequate waste treatment plants to treat their whey effluent. This environmental and regulatory “pressure” would become a constraint to the continued growth of small and medium-sized cheese producers.

Different SW/AW uses have been published anywhere [4,7,8,38-41]. As stated above, SW is very popular for animal feeding due to the important amounts of lactose (4.5-5% (m/v), proteins (0.6-0.8% (m/v)), 0.5% (m/v)) and mineral salts (8-10% on dry basis) [28]. However, as shown in Figure 2, SW/AW has other important uses because it constitutes an important source of proteins isolation [6,16-18,42] one of the most promising SW/AW use nowadays. Several properties such as the high quality of these proteins and their beneficial effects on human and animal health [11,35,36] joined to the simplicity of the process to get them (Figure 3), reinforce the potential of this SW/AW application.

Figure 2: Some uses that may be done to milk whey [15].

Figure 3: The typical membrane-based process to obtain whey protein concentrates or whey powder.

Membrane technology is the most used in SW/AW concentration to produce whey protein concentrates [7,16,20,21,40,43,44]. A typical process is based on successive ultrafiltration steps (UF) and reverses osmosis (RO), followed by concentration by evaporation and a final spray-drier step.

However, using this technology, a deproteinized milk whey permeate lactose-rich is obtained from the ultrafiltration effluent. This lactose –rich byproduct (3.9-4.8% (m/v)) also contains mineral salts, ash (0.3-0.8% (m/v)) and protein traces (0.1-0.3% (m/v)) (39), which gives BOD5 >30 kg m-3 [45] and therefore constitutes a high pollutant which must be treated or used as raw material for other processes. The main cause of its high BOD5 value is lactose, a disaccharide that has several uses in the chemical, food and pharmaceutical industries [46-48].

Microbial-based biotechnological processes to biotransform permeate of whey in valuable products

Despite that lactose excess present in SW/AW is considered as waste, an interesting group of products can be obtained by lactose biotransformation using certain lactose-degrading bacteria and yeast, to produce a broad range of bio products with higher income potentialities than that offered by the original whey [8,15,34,49-52]. By this way, not only can diminish the pollution load of the whey or its permeate but also can increase the business portfolio of dairy companies.

One of them is lactic acid (C3H6O3, CAS L (+): 79-33-4) that has several applications in the food and cosmetic industry [53-56]. L(+) - lactic acid can be obtained from the biotransformation of lactose by Lactobacillus spp. strains, such as Lactobacillus casei [49,53,55,57-60]. This process can be performed by direct microbial transformation in submerged cultures [61-63], or by immobilizing the microbial cells and using a continuous culture in a packing-bed bioreactor with immobilized cells [22,55,64,65], as shown in Figure 4.

Figure 4: Lactic acid production scheme from SW/AW, PW, or PWC by (A) submerged microbial fermentation; (B) immobilized microbial-cells.

The conventional process consists briefly of a fermentation stage where the PW is supplemented with salts and vitamins to achieve the growth of the selected lactic-acid bacteria (LAB) strain (e.g., Lactobacillus casei), keeping the pH close to its optimal growth conditions [56,63]. Subsequently, the biomass obtained and the calcium lactate is separated and washed by differential centrifugation. Calcium lactate is then converted to lactic acid by the addition of sulfuric acid and further separated from the sparingly soluble calcium sulphate. Finally, lactic acid is concentrated by evaporation to about 50% (v/v) (Figure 4A). Another alternative procedure consists in in calcium alginate LAB cells immobilizing in a continuous enzymatic bioreactor to convert the lactate present in PW to lactic acid [22,55,64,66] (Figure 4B).

Also, the lyophilized biomass of L. casei, a recognized probiotic [67], whose intake gives benefits to human health [67-69], could be obtained by a similar process.

Lactose present in SW/AW, PW or PWC could also be used to obtain microbial single-cell protein (SCP), using, for example, the recognized as safe (GRAS status) yeast Kluyveromyces marxianus [10,11]. This yeast can metabolize lactose and reach high cell densities and also is capable of producing significant levels of ethanol [30,70-72], widely used throughout the industry.

A proposed process flow scheme for the production of singlecell protein (SCP) and ethanol from SW/AW, PW or PWC and K. marxianus is shown in Figure 5. Briefly, the process consists of a continuous or semi-continuous fermentation step where the lactose consuming yeast, for example, K. marxianus, growth and secretes ethanol to medium. Subsequently, after thermal inactivation of the microorganism in the culture, the biomass is separated and washed from the supernatant. Finally, the biomass is spray dried, while the ethyl alcohol (technical grade) obtained from the broth supernatant can be recovered by atmospheric distillation [24,72-76].

Figure 5: Process flow scheme for the SCP and ethanol production from SW/AW, PW, or PWC.

Other organic acids, such as propionic acid [23,77,78], butyric acid [79] and citric acid [80] have also been produced by the microbial biotransformation of whey.

Similarly, other alcohols such as butanol have been bio synthesized from certain microbial strains and whey [25,81,82].

Other valuable chemicals derived from whey can be obtained by microbial fermentation such as hydrogen [83-86], polyhydroxyalkanoates [87-89], lipids [90-92], ribonucleotides [93,94], exopolysaccharides [95-97], etc.

Finally, a consortium made up by lactic acid bacteria (LAB) and yeasts, which cohabit within a polymer called kefiran, and which is called a kefir granule, has been used since ancient times to produce a fermented milk called kefir of high nutritional values [98,99] beneficial for human health.

Kefir granules could be used to biotransform the SW/AW, PW or PWC, rich in lactose, to produce kefiran, an edible biopolymer, consisting of units of glucose and galactose in approximately equal proportions [100,101]. Recent studies [102-104] have demonstrated several health-beneficial properties of this biopolymer that make it attractive in drug formulation [104-107] and food preservation [108]. Due to these interesting properties, this edible and biodegradable biopolymer has attracted the researcher’s attention and so, the design of different production process [109]. A proposed process scheme for kefiran production from SW/AW, PW or PWC and kefir granules is shown in Figure 6. Briefly, the process consists in the biotransformation of the lactose present in the PW or PWC, by the existing consortium LAB in the kefir granule. After 48 h fermentation, the culture is homogenized and pasteurized to inactivate the hydrolytic enzymes, the cell debris is subsequently separated, and the soluble kefiran is precipitated with ethanol, the mixture is centrifuged and the precipitate separated, which is subjected to several washes with hot water until the lactose residues are removed. Finally, the kefiran can be dried at 60°C for 24 h [105].

Figure 6: Process flow scheme for the production of kefiran from kefir grain and SW/AW, PW, or PWC.

Enzyme-based biotechnological processes to biotransform permeate of whey in valuable products

Some hydrolytic enzymes, such β-galactosidase (EC 3.2.1.23), could be used to hydrolyze or polymerize lactose, present in SW/ AW, PW or PWC. At concentrations of lactose below 30% (m/v), the hydrolysis of lactose in glucose and galactose predominates [106]; while at higher concentrations the trans-galactosylation reaction and the formation of galacto-oligosaccharides (GOS) could be favored [107,110-112].

Some authors highlight the beneficial effects of GOS on human health [108,109] since they are considered as prebiotic substances [113,114].

In Figures 7A and 7B, the proposed production schemes for both, the hydrolysis of lactose and the formation of GOS, respectively, are shown. Both processes can be performed by immobilizing the enzyme β-galactosidase, which would allow reusing the enzyme and lowering production costs.

Figure 7: Process flow scheme for the enzymatic transformation of SW/AW, PW, or PWC in (A) Hydrolysis of lactose to glucose and galactose; (B) Transgalactosylation of lactose to galactooligosaccharides of different degree of polymerization.

In the case of lactose hydrolysis (Figure 7A), it is favored at concentrations below 30% (w/v) of lactose [26,106,107,113,114]. In this case, the enzymatic hydrolysis reaction is favored yielding the expected products:

Lac⇋Glu+Gal

Where Lac, Glu y Gal represent Lactose (Glu-Gal), glucose and galactose, respectively.

A nano-filtration system can also be coupled to the collector tank to allow the lactose to separate from glucose and galactose. Lactose can be reused, while the glucose and galactose mixture can be concentrated to marketable levels by evaporation.

If lactose concentration is >30-35% (m/v), the trans-galactosylation of lactose would be favored (Figure 7B), and galactooligosaccharides of different polymerization degrees (PD) could be obtained (PD ≥ 2), depending on the number of different species of GOS and the conditions of the enzymatic reaction. For example, if three GOS with different DPs is produced, we would have product yields as follow:

3(n-1)∙Lac ⇌Glu-(Gal)_n+Glu-(Gal)_(n-1)+Glu-(Gal)_(n-2)+3(n- 2)∙Glu

where Glu-(Gal)_n,Glu-(Gal)_(n-1),Glu-(Gal)_(n-2)represent the GOS and n represents the DP of GOS.

Notes for economic feasibility analysis

The valorization of whey is a strategic decision for dairy companies because it eliminates the “bottleneck” that the high volumes generated SW/AW impose on the continuous growth of dairy production. However, it is always desirable that the investment necessary for the implementation of some of the technologies described above, can be amortized and yields gains in reasonable terms.

For the complete economic analysis, each valuation technology, in particular, the predictions of product and sector growth, market demand and the financial availability of dairy companies should be taken into account [115,116].

From 100 kg of whole fresh milk and an average yield of 9.30 ± 0.7 kg in the production of the different kinds of cheeses and the generation of about 90.70 kg of sweet whey [3]. Table 1 compares some of the reported yields and reference prices for a group of available whey technologies.

Process Not treat. WPC SCP WP Glu & Gal Lactic Ac. GOS KEF
Cheeses, TM 9.30 ± 0.7 a
Valorized Product - WPC-34
(34% Prot.)
Single-cell protein Whey dried powder Glucose & Galactose Lactic Acid Galacto-oligosaccharides Kefirán
Qty.2,3, TM - 2.06 2.18 b 5.80 81.63 79.82 c 81.63 0.31 d
Ref. Price - US$1974
/TM e
US$1950
/TM f
US$1100
/TM g
US$600-790 /TM h US$1000 /TM US$20-200
/kg
US$30
/g
Residual SW/AW PW waste water waste water waste water waste water waste water waste water
Qty., TM 90.70 88.64 >88.43 84.90 9.07 >10.88 9.07 >90.38
Lac, %(m/v) 4.8 4.7 0.5 0.1 0.4 0.2 0.2 0.2
COD, kg/m3 i 70 55 6.0 1.2 4.6 2.3 2.3 2.3

Table 1: It is comparative data of some of the whey valorization technologies available. From 100 TM of whole fresh milk.

a Average value [3] . A price is assumed for the cheese curd US$3 764/TM (taken from: http://www.clal.it/en/?section=ricotta, July 24th 2017)

bAssuming a yield Yxs=0.52 TM DB TM lactose-1 [117], so: 0.52* (90.70/1.04)*(48/1000)=2.18 TM and a reduction of 80-90% of COD

cAssuming a 36 h process where 95.6% of the lactose present in the serum (4%) was consumed and a lactic acid concentration of 33.73 g L-1 [63]. So: YPX=33.73/(0.956*40)=0.88 TM Lactic Acid TM lactose-1 and density. @ 80% = 1.2 TM m-3; Vol. syrup @ (80% (m/v)) = 0.88*90.70/0.8 = 99.77m3 syrup.

d Unpublished Result.

e Taken from: http://www.clal.it/en/?section=sieroproteine (July 7th 2017)

f Taken from: https://wholesaler.alibaba.com/product-detail/Manufacture-wholesale-price-instant-dry-yeast_60614513305.html?spm=a2700.7782932.1998701000.11.0W8xnR (July 14th 2017)

g Taken from: http://www.clal.it/en/?section=whey (July 7th 2017)

h Taken from: https://www.alibaba.com/product-detail/Fructose-Glucose-Maltose-rice-syrup-Factory_60669804468.html?spm=a2700.7724838.2017115.231.87bIGj&s=p (17/7/2017)

i Values assumed in proportion to the lactose concentration in the whey permeate (PW) of milk.

The products prices as described below vary from those that are similar to that which would be obtained from the commercialization of the fresh milk itself. It means 8.3 kg fluid milk kg whole milk powder-1, therefore: 100 TM fluid milk equivalents to 12 TM of approximately whole milk powder and whose price is US $ 3 200 per TM, to those that exceed two digits to that of milk (Figure 8).

Figure 8: It is a comparison of some of the existing technologies for the valorization of whey. The dashed line represents the price of whole milk powder obtained from processing 100 TM of whole fresh milk.

These values allow classifying whey recovery technologies, in those that provide low, medium and high income (Figure 8).

Also, during the valorization process of whey, it is possible to reduce significantly the contaminant load of the effluents, which is one of the main reasons for the implementation of these technologies. From effluents requiring a primary, secondary and tertiary treatments (for the treatment of SW/AW and PW), to less polluting effluents, presumably requiring only primary treatment, which would reduce the costs of treatment in the dairy companies.

Conclusion Remarks

Zone 1 of Ecuador and specifically the provinces of Carchi and Imbabura are purely livestock and cheese producers. An important part of the economically active population of these provinces is dedicated to the production and commercialization of cheeses, prevailing small and medium producers. With the increment of environmental regulations together with the gradually ecological conscience of producers, it becomes more difficult to pour, dairy surplus and significant amounts of whey in rivers, lakes and streams. Therefore, the growth of the dairy and cheese sector of small and medium producers is limited by the high volumes of milk whey this would bring, due to the high COD and BOD values of this by-product.

An alternative is to seek to reduce the impact of effluents by searching for technologies that use whey as the starting raw material, as discussed below in this review.

However, to implement these technologies, it is essential to undertake an investment process and to have certain financial resources that are hardly available in small and medium milk and cheese producers, even if they may eventually be associated in cooperatives for these purposes.

A possible solution is to find out external funds from the private or state sector. Also, to establish public-private partnerships that allow access to financial resources and encourage entrepreneurship, and so that, it can stimulate and foster increases in future of milk production among small and medium producers in Zone 1 and all over Ecuador.

The Academy including Universities, Technical Institutes and Research Centers, on the other hand, could contribute to the required studies, the developments and the most appropriate technologies, as well as in the formation of the entrepreneurs that can undertake these projects. All these efforts, as a whole, could be combined to guarantee the continuous growth of milk production in Zone 1 of Ecuador in the forthcoming years, in the way shown in Figure 9.

Figure 9: Interrelations that will enable the continued growth of Dairy production to small and medium-sized producers by eliminating the limitations that the high volumes of milk whey may exercise on growth in the production of milk and cheeses.

Also, with the new facilities, new job sources would be generated, current imports would be replaced, and the productive matrix of Ecuador would be changing and expanding.

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