Cheese whey processing: integrated biorefinery concepts and emerging food applications

Cheese whey constitutes one of the most polluting by-products of the food industry, due to its high organic load. Thus, in order to mitigate the environmental concerns, a large number of valorization approaches have been reported; mainly targeting the recovery of whey proteins and whey lactose from cheese whey for further exploitation as renewable resources. Most studies are predominantly focused on the separate implementation, either of whey protein or lactose, to configure processes that will formulate value-added products. Likewise, approaches for cheese whey valorization, so far, do not exploit the full potential of cheese whey, particularly with respect to food applications. Nonetheless, within the concept of integrated biorefinery design and the transition to circular economy, it is imperative to develop consolidated bioprocesses that will foster a holistic exploitation of cheese whey. Therefore, the aim of this article is to elaborate on the recent advances regarding the conversion of whey to high value-added products, focusing on food applications. Moreover, novel integrated biorefining concepts are proposed, to inaugurate the complete exploitation of cheese whey to formulate novel products with diversified end applications. Within the context of circular economy, it is envisaged that high value-added products will be reintroduced in the food supply chain, thereby enhancing sustainability and creating “zero waste” processes

Mediterranean raisins/currants as traditional superfoods: processing, health benefits, food applications and future trends within the bio-economy era

This review elaborates on the significance of Mediterranean raisins, focusing particularly on indigenous Greek varieties (e.g., Zante currants) as a previously overlooked traditional food, currently brought on the spotlight, resulting from the increased consumers’ awareness to improve wellness through diet modification. Recent studies on the effect of processing steps on final quality, along with findings on the potential health benefits raisins and currants elicit, are also presented. The development of novel functional food products to further exploit the nutritional value and the bioactive compounds of raisins is evidenced in view of indicating potential food industry applications. Moreover, valorization options of waste and by-product streams obtained from processing facilities are also proposed. Conclusively, raisins and currants should be further enhanced and incorporated in a balanced diet regime through the inclusion in novel foods formulation. Evidently, both the processing of the onset material and side-streams management, are essential to ensure sustainability. Hence, the article also highlights integrated biorefinery approaches, targeting the production of high-value added products that could be re-introduced in the food supply chain and conform with the pillars of bio-economy

A Comprehensive Bioprocessing Approach to Foster Cheese Whey Valorization: On-Site β-Galactosidase Secretion for Lactose Hydrolysis and Sequential Bacterial Cellulose Production

Cheese whey (CW) constitutes a dairy industry by-product, with considerable polluting impact, related mostly with lactose. Numerous bioprocessing approaches have been suggested for lactose utilization, however, full exploitation is hindered by strain specificity for lactose consumption, entailing a confined range of end-products. Thus, we developed a CW valorization process generating high added-value products (crude enzymes, nutrient supplements, biopolymers). First, the ability of Aspergillus awamori to secrete β-galactosidase was studied under several conditions during solid-state fermentation (SSF). Maximum enzyme activity (148 U/g) was obtained at 70% initial moisture content after three days. Crude enzymatic extracts were further implemented to hydrolyze CW lactose, assessing the effect of hydrolysis time, temperature and initial enzymatic activity. Complete lactose hydrolysis was obtained after 36 h, using 15 U/mL initial enzymatic activity. Subsequently, submerged fermentations were performed with the produced hydrolysates as onset feedstocks to produce bacterial cellulose (5.6–7 g/L). Our findings indicate a novel approach to valorize CW via the production of crude enzymes and lactose hydrolysis, aiming to unfold the output potential of intermediate product formation and end-product applications. Likewise, this study generated a bio-based material to be further introduced in novel food formulations, elaborating and conforming with the basic pillars of circular economy

Monitoring the Temporal Expression of Genes Involved in Ochratoxin A Production of Aspergillus carbonarius under the Influence of Temperature and Water Activity

The objective of this study was to investigate the effect of environmental factors, namely temperature and water activity, on genes involved in the regulation of ochratoxin A (OTA) production over time. For this purpose, the previously characterized toxigenic Aspergillus carbonarius Ac29 isolate from Greek vineyards and the A. carbonarius ITEM 5010 reference strain were subjected to combined temperature and water activity (aw) treatments to study OTA production and relative gene expression. The fungal isolates were grown on a synthetic grape juice liquid medium (SGM) under different temperature (20 °C, 25 °C and 30 °C) and aw (0.94 and 0.98) regimes. The expression of the AcOTApks, AcOTAnrps, and laeA OTA related genes was investigated using real time PCR. Gene expression was monitored at the same time points, along with fungal biomass and OTA accumulation at three, six and nine days of incubation. In gene expression analysis, stimulation of the biosynthetic genes was observed a few days before any toxin could be detected. This fact may underline a possible early indicator of potential toxin contamination of grapes. However, the transcript levels varied with respect to the different combinations of ecophysiological conditions and time, highlighting a complex regulation of OTA related gene expression of A. carbonarius in the specific medium

Dual Transcriptional Profile of Aspergillus flavus during Co-Culture with Listeria monocytogenes and Aflatoxin B1 Production: A Pathogen–Pathogen Interaction

The objective of this study was to investigate the effect of growth temperature and co-culture of Aspergillus flavus with Listeria monocytogenes on the production of Aflatoxin B1 (AFB1) and the transcriptional profile of associated regulatory and biosynthetic genes. The transcription of virulence- and homeostasis-associated genes of L. monocytogenes was also assessed. For this purpose, mono- and co-cultures of L. monocytogenes strain LQC 15257 and A. flavus strain 18.4 were inoculated into Malt Extract broth and allowed to grow for seven days at 25 °C and 30 °C. AFB1 quantification was performed by HPLC analysis and gene expression assessment by RT-qPCR. AFB1 production was lower at 30 °C compared to 25 °C during monoculture and also lower during co-cultures at both temperatures. This was accompanied by downregulation of aflM, aflR, aflP, and aflS during monoculture and aflM and aflS during co-culture at 30 °C. On the other hand, transcription of prfA, plcA, plcB, inlA, inlB, inlJ, murE, accA, acpP, as well as fapR, was not affected. sigB gene was downregulated after co-culture with the fungus at 25 °C and hly was downregulated after monoculture at 30 °C compared to 25 °C. In this work, the molecular interactions between A. flavus and L. monocytogenes were studied for the first time, offering a novel insight into their co-occurrence. Monitoring of their toxigenic and virulence potential at the molecular level revealed a complex dynamic in natural ecosystems