Strategies for maximizing removal of lactic acid from acid whey – Addressing the un-processability issue

Exclusive D-lactate-isomer production during a reactor-microbiome conversion of lactose-rich waste by controlling pH and temperature

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.

Unraveling the Influences of Sodium, Potassium, Magnesium, and Calcium on the Crystallization Behavior of Lactose

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.

Transforming acid whey into a resource by selective removal of lactic acid and galactose using optimized food-grade microorganisms

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.

Food waste biorefinery towards circular economy in Australia

Staggering amounts of food waste are produced in Australia, and this review provides food waste based biorefinery opportunities in moving towards a circular economy in Australia. The current food waste scenario in Australia including an overview of primary food waste sources, government regulation, and current management practices is presented. The major food waste streams include fruit and vegetable (waste from wine grapes, citrus, apple, potato, and tomato), nuts (almond processing waste), seafood (Fish waste), dairy whey, sugarcane bagasse, and household and businesses. The composition of these waste streams indicated their potential for use in biorefineries to produce value-added products via various pathways combining direct extraction and biological and thermochemical conversion. Finally, the efforts made in Australia to utilize food waste as a resource, as well as the challenges and future directions to promote the development of concrete and commercially viable technologies for food waste biorefinery, are described.

Enrichment of Lactoferrin and Immunoglobulin G from Acid Whey by Cross-Flow Filtration

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.

Modeling of lactic acid rejection from lactose in acidified cheese whey by nanofiltration

The continuously increasing demand of lactic acid opens a window for the integration of membrane technology in the dairy industry, improving the sustainability by avoiding the use of large amounts of chemicals and waste generation. Lactic acid recovery from fermentation broth without precipitation has been studied by numerous processes. In this work, a commercial membrane with high lactose rejection and a moderate lactic acid rejection, enabling a permselectivity up to 40%, is sought to perform the simultaneous removal of lactic acid and lactose separation from the acidified sweet whey from mozzarella cheese production in a single stage. The AFC30 membrane of the thin film composite nanofiltration (NF) type was selected because of its high negative charge, low isoelectric point, and divalent ion rejection, as well as a lactose rejection higher than 98% and a lactic acid rejection lower than 37%, at pH 3.5, to minimize the need of additional separation steps. The experimental lactic acid rejection was evaluated at varying feed concentration, pressure, temperature, and flow rate. As the dissociation degree of lactic acid is negligible in industrially simulated conditions, the performance of this NF membrane was validated by the irreversible thermodynamic Kedem-Katchalsky and Spiegler-Kedem models, with the best prediction in the latter case, with the parameter values: L_p = 3.24 ± 0.87 L × m^-2 × h^-1 × bar^-1 and = 15.06 ± 3.17 L × m^-2 × h^-1, and σ = 0.45 ± 0.03. The results obtained in this work open the way for the up-scaling of membrane technology on the valorization of dairy effluents by simplifying the operation process and the model prediction and the choice of the membrane.

Whey-based polymeric films for food packaging applications: a review of recent trends

The food industry is always looking for new strategies to extend the shelf life of food. In recent years, the focus has been on edible films and coatings. These play an essential role in the quality, safety, transport, storage, and display of a wide variety of fresh and processed foods and contribute to environmental sustainability. In this sense, this study aimed to carry out a bibliometric analysis and literature review on the production of whey-based films for application in food packaging. Whey-based films have different characteristics when compared to other biopolymers, such as antimicrobial and immunomodulatory capacity. A wide variety of compounds were found that can be incorporated into whey films, aiming to overcome their limitations related to high solubility and low mechanical properties. These compounds range from plasticizing agents, secondary biomacromolecules added to balance the polymer matrix (gelatin, starch, chitosan), and bioactive agents (essential oils, pigments extracted from plants, and other antimicrobial agents). The most cited foods as application matrix were meat (fish, chicken, ham, and beef), in addition to different types of cheese. Edible and biodegradable films have the potential to replace synthetic polymers, combining social, environmental, and economic aspects. The biggest challenge on a large scale is the stability of physical, chemical, and biological properties during application. © 2022 Society of Chemical Industry.

The Performance of Ultrafiltration Process to Further Refine Lactic Acid from the Pre-Microfiltered Broth of Kitchen Waste Fermentation

Lactic acid (LA) is an important chemical material facing rapid demand in recent years. The oriented fermentation of kitchen waste is a promising route for economic LA production. However, the refinement of LA from fermentation broth is a spiny issue. In this study, the performance of ultrafiltration (UF) process for the refinement of LA from the pre-microfiltered broth of kitchen waste fermentation was first investigated. The results showed that with 50 KDa polyethersulfone membrane, under the optimum pressure of 120 KPa, the pH of 6.0, and the backflushing mode with the deionized water for 3 min, the best performance was achieved with the chroma removal efficiency, turbidity removal efficiency, protein removal efficiency and total sugar removal efficiency of 54.3%, 89.8%, 71.7% and 58.5%, respectively, and LA recovery efficiency was 93.6%. The results indicated that the UF process could further effectively refine the pre-microfiltered broth of kitchen waste fermentation, and the combination of microfiltration and UF process is ideal for achieving desirable LA refinement performance. This study verified the feasibility of UF process in LA refinement from pre-microfiltered broth of kitchen waste fermentation, and based on the results, the further exploration of proper post-process to treat UF filtrate for obtaining LA product with higher quality should be explored in the future.

Nanofiltration of the Remaining Whey after Kefir Grains' Cultivation

Acid whey is derived from fresh cheese. The proteins were isolated by a monolithic ion-exchange column. The remaining whey fraction was used as a starter culture substrate of kefir grains. The aim of this work was, firstly, to study the possibility of column replacement by a UF membrane. If we succeeded, the concentrate would be used as a starter culture substrate of kefir grains. The second part of the research was to purify the remaining solution. The idea was to separate this solution to the permeate and the concentrate by nanofiltration. Further application of both filtration streams was tested as aqueous solutions or dried matter. Chemical and microbiological analyses were performed of both the permeate and the concentrate. The permeate analyses showed that lactose had been fully removed. The aqueous permeate was not stable, mainly due to an increase of total bacteria from 10³ to 10⁶ CFU/mL. Therefore, the permeate was spray-dried. The dry permeate was added to the moisture solution in different concentrations. The results showed that up to 0.5% of the dry permeate could be added to the moisturizing solution, with negligible changes in properties having the ability to inhibit acne growth. Anaerobic digestion of industrial sludge was performed with the addition of an aqueous concentrate, which showed improvement in anaerobic fermentation.

Membrane technologies for sports supplementation

The important developments in membrane techniques used in the dairy industrial processes to whey manufacturing are discussed. Particular emphasis is placed on the description of membrane processes, characterization of protein products, biological issues related to bacteriophages contamination, and modeling of the processes. This choice was dictated by the observed research works and consumer trends, who increasingly appreciate healthy food and its taste qualities.

Use of Membrane Technologies in Dairy Industry: An Overview

The use of treatments of segregated process streams as a water source, as well as technical fluid reuse as a source of value-added recovery products, is an emerging direction of resource recovery in several applications. Apart from the desired final product obtained in agro-food industries, one of the challenges is the recovery or separation of intermediate and/or secondary metabolites with high-added-value compounds (e.g., whey protein). In this way, processes based on membranes, such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), could be integrated to treat these agro-industrial streams, such as milk and cheese whey. Therefore, the industrial application of membrane technologies in some processing stages could be a solution, replacing traditional processes or adding them into existing treatments. Therefore, greater efficiency, yield enhancement, energy or capital expenditure reduction or even an increase in sustainability by producing less waste, as well as by-product recovery and valorization opportunities, could be possible, in line with industrial symbiosis and circular economy principles. The maturity of membrane technologies in the dairy industry was analyzed for the possible integration options of membrane processes in their filtration treatment. The reported studies and developments showed a wide window of possible applications for membrane technologies in dairy industry treatments. Therefore, the integration of membrane processes into traditional processing schemes is presented in this work. Overall, it could be highlighted that membrane providers and agro-industries will continue with a gradual implementation of membrane technology integration in the production processes, referring to the progress reported on both the scientific literature and industrial solutions commercialized.

Bacterial Diversity Analysis and Evaluation Proteins Hydrolysis During the Acid Whey and Fish Waste Fermentation

The disposal of acid whey (Aw), a by-product from fermented products, is a problem for the dairy industry. The fishery industry faces a similar dilemma, disposing of nearly 50% of fish processed for human consumption. Economically feasible and science-based alternatives are needed to overcome this problem. One possible solution is to add value to the remaining nutrients from these by-products. This study focuses on the breakdown of nutrients in controlled fermentations of Aw, fish waste (F), molasses (M), and a lactic acid bacteria (LAB) strain (Lr). The aim was to assess the dynamic variations in microbial diversity and the biochemical changes that occur during fermentation. Four treatments were compared (AwF, AwFM, AwFLr, and AwFMLr), and the fermentation lasted 14 days at 22.5 °C. Samples were taken every other day. Colorimetric tests for peptide concentrations, pH, and microbial ecology by 16S-v4 rRNA amplicon using Illumina MiSeq were conducted. The results of the microbial ecology showed elevated levels of alpha and beta diversity in the samples at day zero. By day 2 of fermentation, pH dropped, and the availability of a different set of nutrients was reflected in the microbial diversity. The fermentation started to stabilize and was driven by the Firmicutes phylum, which dominated the microbial community by day 14. Moreover, there was a significant increase (3.6 times) in peptides when comparing day 0 with day 14, making this treatment practical and feasible for protein hydrolysis. This study valorizes two nutrient-dense by-products and provides an alternative to the current handling of these materials.

Batch and Continuous Lactic Acid Fermentation Based on A Multi-Substrate Approach

The utilisation of waste materials and industrial residues became a priority within the bioeconomy concept and the production of biobased chemicals. The aim of this study was to evaluate the feasibility to continuously produce L-lactic acid from different renewable substrates, in a multi-substrate strategy mode. Based on batch experiments observations, Bacillus coagulans A534 strain was able to continuously metabolise acid whey, sugar beet molasses, sugar bread, alfalfa press green juice and tapioca starch. Additionally, reference experiments showed its behaviour in standard medium. Continuous fermentations indicated that the highest productivity was achieved when molasses was employed with a value of 10.34 g·L⁻¹·h⁻¹, while the lactic acid to sugar conversion yield was 0.86 g·g⁻¹. This study demonstrated that LA can be efficiently produced in continuous mode regardless the substrate, which is a huge advantage in comparison to other platform chemicals.