In the field of biotechnology, the utilization of agro-industrial waste for generating high-value products, such as microbial biomass and enzymes, holds significant importance. This study aimed to produce recombinant α-amylase from Anoxybacillus karvacharensis strain K1, utilizing whey as an useful growth medium. The purified hexahistidine-tagged α-amylase exhibited remarkable homogeneity, boasting a specific activity of 1069.2 U mg-1. The enzyme displayed its peak activity at 55 °C and pH 6.5, retaining approximately 70% of its activity even after 3 h of incubation at 55 °C. Its molecular weight, as determined via SDS-PAGE, was approximately 69 kDa. The α-amylase demonstrated high activity against wheat starch (1648.8 ± 16.8 U mg-1) while exhibiting comparatively lower activity towards cyclodextrins and amylose (≤ 200.2 ± 16.2 U mg-1). It exhibited exceptional tolerance to salt, withstanding concentrations of up to 2.5 M. Interestingly, metal ions and detergents such as sodium dodecyl sulfate (SDS), Triton 100, Triton 40, and Tween 80, 5,5\'-dithio-bis-[2-nitrobenzoic acid (DNTB), β-mercaptoethanol (ME), and dithiothreitol (DTT) had no significant inhibitory effect on the enzyme\'s activity, and the presence of CaCl2 (2 mM) even led to a slight activation of the recombinant enzyme (1.4 times). The Michaelis constant (Km) and maximum reaction rate (Vmax), were determined using soluble starch as a substrate, yielding values of 1.2 ± 0.19 mg mL-1 and 1580.3 ± 183.7 μmol mg-1 protein min-1, respectively. Notably, the most favorable conditions for biomass and recombinant α-amylase production were achieved through the treatment of acid whey with β-glucosidase for 24 h.

Bacterial cellulose (BC, biocellulose) is a natural polymer of microbiological origin that meets the criteria of a biomaterial for food packaging. The aim of the research was to obtain biocellulose and test its chemical as well as physical characterization as a potential packaging for Dutch-type cheeses. Four variants of biocellulose-based material were obtained: not grinded and grinded variants obtained from YPM medium (YPM-BCNG and YPM-BCG, respectively) and not grinded and grinded variants from acid whey (AW) (AW-BCNG and AW-BCG, respectively). It was demonstrated that AW-BCNG exhibited the highest thermostability and the highest degradation temperature (348 °C). YPM-BCG and YPM-BCNG demonstrated higher sorption properties (approx. 40 %) compared to AW-BCG and AW-BCNG (approx. 15 %). Cheese packaged in biocellulose (except for YPM-BCNG) did not differ in water, fat, or protein content compared to the control cheese. All of the biocellulose packaging variants provided the cheeses with protection against unfavourable microflora. It was demonstrated that cheeses packaged in biocellulose were characterized by lower hardness, fracturability, gumminess, and chewiness than the control cheese sample. The results obtained indicate that BC may be a suitable packaging material for ripening cheeses, which shows a positive impact on selected product features.

This work describes the preparation of a novel biopolymer hydrogel based on acid whey, cellulose derivatives and polyvinyl alcohol (PVA). The hydrogel was prepared and characterized with the aim of producing an environmentally-friendly soil amendment to increase water retention capacity of the soil. The findings showed considerable swelling properties of the hydrogels depending on the PVA content and crosslinking density. The samples with PVA in a concentration 2.5 % and 5 % were more rigid, the gel fraction increased with a subsequently decrease in their swelling capacity. The hydrogels crosslinked with 15 % of citric acid demonstrated a constant swelling ratio (SR) of around 500 % within 10 swelling/drying cycles. The hydrogels crosslinked with 10 % citric acid and supplemented with 1 % of PVA showed SR of 1000-1400 % caused by less crosslinked polymer network and increased pore volume for water uptake. It was found that hydrogel with a higher gel fraction had a stable structure. Supplementing PVA at 5 % extended the period of decomposition of the hydrogel material by almost 60 % in the soil environment and soil humidity was maintained for longer. Applying 2 % of the hydrogel 5PVA to soil increased the water retention capacity by 19 %.

Lactate is among the top-ten-biobased products. It occurs naturally as D- or L-isomer and as a racemic mixture (DL-lactate). Generally, lactate with a high optical purity is more valuable. In searching for suitable renewable feedstocks for lactate production, unutilized organic waste streams are increasingly coming into focus. Here, we investigated acid whey, which is a lactose-rich byproduct of yogurt production, that represents a considerable environmental footprint for the dairy industry. We investigated the steering of the lactate-isomer composition in a continuous and open culture system (HRT = 0.6 d) at different pH values (pH 5.0 vs. pH 6.5) and process temperatures (38°C to 50°C). The process startup was achieved by autoinoculation. At a pH of 5.0 and a temperature of 47°C-50°C, exclusive D-lactate production occurred because of the dominance of Lactobacillus spp. (> 95% of relative abundance). The highest volumetric D-lactate production rate of 722 ± 94.6 mmol C L-1 d-1 (0.90 ± 0.12 g L-1 h-1), yielding 0.93 ± 0.15 mmol C mmol C-1, was achieved at a pH of 5.0 and a temperature of 44°C (n = 18). At a pH of 6.5 and a temperature of 44°C, we found a mixture of DL-lactate (average D-to-L-lactate production rate ratio of 1.69 ± 0.90), which correlated with a high abundance of Streptococcus spp. and Enterococcus spp. However, exclusive L-lactate production could not be achieved. Our results show that for the continuous conversion of lactose-rich dairy waste streams, the pH was a critical process parameter to control the yield of lactate isomers by influencing the composition of the microbiota. In contrast, temperature adjustments allowed the improvement of bioprocess kinetics.

The inability of lactose to properly crystallize due to the presence of high amounts of salts poses significant hurdles for its downstream processing with some dairy waste streams such as acid whey. This study aimed to investigate the physicochemical and thermal behaviors of lactose in the presence of cations commonly present in acid whey. A model-based study was conducted, utilizing various cations (Mg, Ca, K, and Na) at concentrations (8, 30, 38, and 22 mM, respectively) that are typically found in acid whey. The research experiments were conducted using a factorial design. The thermal analysis of concentrated solutions revealed augmentation in the enthalpy of water evaporation in the presence of individual cations and their combinations in comparison with pure lactose (698.4 J/g). The degree of enthalpy increased following the order of Na+ (918.6 J/g), K+ (936.6 J/g), Mg2+ (987.0 J/g), Ca2+ (993.2 J/g), and their mixture (1005.4 J/g). This resulted in a substantial crystal yield decline in the exactly reversed order to that of the enthalpy. The greatest decline was observed in the presence of the salt mixture (63%) followed by Ca (67%) compared with pure lactose (79%). The yield reduction was also inversely related to the solubility of lactose. The presence of divalent cations appeared to play a role in the isomerization of lactose molecules observed using DSC and XRD diffractograms according to the disappearance of peaks related to β lactose. The effect of salts on the crystallization of lactose was a combination of cation-lactose interactions, changes in the solubility of lactose, ion-dipole interactions between water and cations, and changes in the structure of water molecules. By deviating the composition of acid whey, the crystallization of lactose can be enhanced, leading to the improved downstream processing of acid whey.

The aim of this study was to evaluate the influence of in acid whey (AW) multiplied Lactiplantibacillus plantarum LUHS135 (L.pl135), Lacticaseibacillus paracasei LUHS244 (L.pc244), and their biomass combination on newborn calves\' feces and blood parameters. Additionally, the antimicrobial and mycotoxin-reducing properties and the resistance to antibiotics of the tested lactic acid bacteria (LAB) strains were analyzed. In order to ensure effective biomass growth in AW, technological parameters for the supplement preparation were selected. Control calves were fed with a standard milk replacer (SMR) and treated groups (from the 2nd day of life until the 14th day) were supplemented with 50 mL of AWL.pl135, AWL.pc244, and AWL.pl135×L.pc244 (25 mL AWL.pl135 + 25 mL AWL.pc244) in addition to SMR. It was established that L.pl135 and L.pc244 possess broad antimicrobial activities, are non-resistant to the tested antibiotics, and reduce mycotoxin concentrations in vitro. The optimal duration established for biomass growth was 48 h (LAB count higher than 7.00 log10 CFU mL-1 was found after 48 h of AW fermentation). It was established that additional feeding of newborn calves with AWL.pl135, AWL.pc244, and AWL.pl135×L.pc244 increased lactobacilli (on average by 7.4%), and AWL.pl135 and AWL.pc244 reduced the numbers of Enterobacteriaceae in calves\' feces. The tested supplements also reduced the lactate concentration (on average, by 42.5%) in calves\' blood. Finally, the tested supplements had a positive influence on certain health parameters of newborn calves; however, further research is needed to validate the mechanisms of the beneficial effects.

Yogurt acid whey (YAW), a by-product of strained yogurt production, is a strong environmental pollutant because of its high organic load. Hence, efforts are made for its utilization to minimize its disposal in the environment. This study deals with the incorporation of YAW in yogurt ice cream (YIC) by partial replacement of yogurt with simultaneous lactose hydrolysis (LH) of the formulated YIC mix. Six YIC mix formulations were made, two without YAW (non-LH- and LH-control samples, A and AH), two with 12.5% YAW (samples B and BH), and two with 18.75% YAW (samples C and CH). The results showed that the partial replacement of yogurt with YAW decreased significantly (p < 0.05) the total solids of B, BH, C, and CH products (31.72 ± 0.14%, 31.92 ± 0.21%, 30.94 ± 0.14%, and 31.27 ± 0.10%, respectively) compared to the total solids of control products A and AH (33.30 ± 0.36% and 33.74 ± 0.06%, respectively). In contrast, the overruns increased (51.50 ± 2.36%, 58.26 ± 0.09%, 56.86 ± 1.92%, and 65.52 ± 1.30% for the B, BH, C, and CH products, respectively) compared to control samples (42.02 ± 2.62% and 49.53 ± 2.12% for A and AH, respectively). LH significantly decreased the freezing point and the viscosity of the YIC mixes but increased the overruns of the products as shown previously. YAW significantly decreased the hardness of the B and C products (56.30 ± 2.11 N and 43.43 ± 3.91 N, respectively) compared to control A (81.14 ± 9.34 N), and LH decreased it even more, leading to a rather soft scoop YIC. AH, BH, and CH YICs exhibited better melting properties despite the lack of fat destabilization in all samples. After 60 days of storage, counts of yogurt starter microorganisms were still >107 cfu/g and DPPH radical scavenging activity had increased in all products. In the sensory evaluation test, lactose-hydrolyzed samples AH, BH, and CH had less intense sandiness and, as expected, more intense sweetness. In conclusion, in the framework of the circular economy, it is possible for the YAW to be used as a resource material at a ratio of 12.5% to produce a YIC product without leaving behind any new waste.

In recent years, the increasing demand for Greek strained yoghurt produced massive amounts of acid whey, which constitutes a major environmental pollutant. Whether yoghurt acid whey can be included in poultry diets is not known. The purpose of this study was to evaluate the effects of four dietary levels of yoghurt acid whey powder (YAWP) on the growth performance, nutrient digestibility, meat quality traits and oxidative stability. A total of 300 male 1-day-old Ross 308 broilers were assigned into four groups with five replicates of 15 broilers each: control-fed basal diet with no YAWP addition (WO) or basal diet supplemented with YAWP at 25 g/kg of diet (WA), 50 g/kg of diet (WB), or 100 g/kg of diet (WC). At the starter period, body weight and body weight gain were reduced after WB and WC treatments compared to the WO treatment. Breast meat oxidative stability was improved during refrigerated storage for 1 and 3 d in all YAWP treatments compared to control, while the WA treatment showed an improved oxidative stability after 6 and 9 d. The results suggest that YAWP inclusion at 25 g/kg of diet did not impair performance and extended the meat shelf life by reducing lipid oxidation rates.

The presence of lactic acid and galactose makes spray drying of acid whey (AW) a significant challenge for the dairy industry. In this study, a novel approach is explored to remove these compounds, utilizing food-grade microorganisms. For removing lactic acid, Corynebacterium glutamicum was selected, which has an inherent ability to metabolize lactic acid but does so slowly. To accelerate lactic acid metabolism, a mutant strain G6006 was isolated through adaptive laboratory evolution, which metabolized all lactic acid from AW two times faster than its parent strain. To eliminate galactose, a lactose-negative mutant of Lactococcus lactis that cannot produce lactate was generated. This strain was then co-cultured with G6006 to maximize the removal of both lactic acid and galactose. The microbially \"filtered\" AW could readily be spray dried into a stable lactose powder. This study highlights the potential of utilizing food-grade microorganisms to process AW, which currently constitutes a global challenge.

The production of cream cheese, curd, high-protein yogurt, or caseinate results in large amounts of acid whey as a by-product. So far acid whey is often disposed as animal feed or organic fertilizer. However, these approaches ignore the valorization potential that arises from the unique composition of the whey protein fraction. Whey contains the biofunctional proteins lactoferrin and immunoglobulin G, which possess immune-supporting, antibacterial, antiviral, and numerous further health-promoting functions. However, the concentration of these proteins in bovine milk or whey is below a physiologically relevant level. Based on literature research we specified a daily intake of 200 mg lactoferrin as the minimal functional dose. By means of cross-flow ultrafiltration, an attempt was made to increase the concentration of biofunctional proteins. Therefore, a membrane for the selective retention of lactoferrin and immunoglobulin G was identified, and the process parameters were optimized. Finally, a concentration experiment was conducted, whereby the concentration of biofunctional proteins was increased up to factor 30. The biofunctionality was assessed in a microbiological assay. Surprisingly, the antimicrobial growth inhibition of the produced concentrate was even higher than in pure lactoferrin. The presented approach offers a strategy to convert an abundant but underutilized by-product into valuable products for human nutrition.