Life cycle assessment (LCA) of end-of-life dairy products (EoL-DPs) valorization via anaerobic co-digestion with agro-industrial wastes for biogas production

BACKGROUND: The aim of the present study was to assess the environmental impacts of End-of-Life Dairy Products (EoL-DPs) management via their co-treatment with agro-industrial wastes (AgW) in a centralized biogas facility located in Cyprus using a gate-to-gate LCA approach. Two different scenarios were examined under the framework of this project. In the first one, co-treatment of EoL-DPs with various AgW (in a 20/80, w/w, ratio) was evaluated in a one-stage mesophilic anaerobic digestion (AD) process. In the second scenario, the same amount of EoL-DPs were acidified before methanogenesis with AgW in order to improve biogas production. RESULTS: Prior acidification of EoL-DPs showed a better environmental performance compared to the results obtained upon direct co-digestion in a mesophilic digester, having a total impact of 52.44 Pt against 57.13 Pt respectively. Biogas production upon acidification, and therefore energy yield, was higher reaching up to 22.88 m3 CH4/ton of feed (229.25 kWh/ton of feed), compared to 17.45 m3 CH4/on of feed (174.85 kWh/ton of feed) for the case where no pretreatment was performed. CONCLUSIONS: The acidification of EoL-DPs enhanced the environmental performance of the process by reducing its impact by 8.2% (in Pt equivalents). The energy consumption of the biogas plant mixing equipment was identified as the process hotspot. However, further analysis of the environmental performance of the proposed process is required by extending the system’s boundaries towards a Cradle-to-Grave approach

Valorisation of side streams from wheat milling and confectionery industries for consolidated production and extraction of microbial lipids

Crude enzymes produced via solid state fermentation (SSF) using wheat milling by-products have been employed for both fermentation media production using flour-rich waste (FRW) streams and lysis of Rhodosporidium toruloides yeast cells. Filter sterilization of crude hydrolysates was more beneficial than heat sterilization regarding yeast growth and microbial oil production. The initial carbon to free amino nitrogen ratio of crude hydrolysates was optimized (80.2 g/g) in fed-batch cultures of R. toruloides leading to a total dry weight of 61.2 g/L with microbial oil content of 61.8 % (w/w). Employing a feeding strategy where the glucose concentration was maintained in the range of 12.2 – 17.6 g/L led to the highest productivity (0.32 g/L∙h). The crude enzymes produced by SSF were utilised for yeast cell treatment leading to simultaneous release of around 80% of total lipids in the broth and production of a hydrolysate suitable as yeast extract replacement

Rhodosporidium toruloides cultivated in NaCl-enriched glucose-based media: adaptation dynamics and lipid production

In the present report and for the first time in the international literature, the impact of the addition of NaCl upon growth and lipid production on the oleaginous yeast Rhodosporidium toruloides was studied. Moreover, equally for first time, lipid production by R. toruloides was performed under non-aseptic conditions. Therefore, the potentiality of R. toruloides DSM 4444 to produce lipid in media containing several initial concentrations of NaCl with glucose employed as carbon source was studied. Preliminary batch-flask trials with increasing amounts of NaCl revealed the tolerance of the strain against NaCl content up to 6.0% (w/v). However, 4.0% (w/v) of NaCl stimulated lipid accumulation for this strain, by enhancing lipid production up to 71.3% (w/w) per dry cell weight. The same amount of NaCl was employed in pasteurized batch-flask cultures in order to investigate the role of the salt as bacterial inhibiting agent. The combination of NaCl and high glucose concentrations was found to satisfactorily suppress bacterial contamination of R. toruloides cultures under these conditions. Batch-bioreactor trials of the yeast in the same media with high glucose content (up to 150 g/L) resulted in satisfactory substrate assimilation, with almost linear kinetic profile for lipid production, regardless of the initial glucose concentration imposed. Finally, fed-batch bioreactor cultures led to the production of 37.2 g/L of biomass, accompanied by 64.5% (w/w) of lipid yield. Lipid yield per unit of glucose consumed received the very satisfactory value of 0.21 g/g, a value amongst the highest ones in the literature. The yeast lipid produced contained mainly oleic acid and to lesser extent palmitic and stearic acids, thus constituting a perfect starting material for “second generation” biodiese

Trametes versicolor as a Natural Source of Bioactive Compounds for the Production of Whey Protein Films with Functional Properties: A Holistic Approach to Valorize Cheese Whey

Purpose: Cheese whey (CW) protein and lactose fractions were individually valorized in the direction of functional food development, employing a newly isolated Trametes versicolor strain from Kefalonia Island (Greece). Methods: T. versicolor growth was evaluated on solid-state fermentations, using potato dextrose agar (PDA), whereas submerged fermentations were employed under static and agitated conditions, using pure lactose and CW-lactose fraction as fermentation media. Subsequently, whey protein fraction was utilized for edible films production supplemented by the freeze-dried fungal biomass. Edible films properties were further characterized concerning their thickness, water-related properties, protein composition and antioxidant capacity. Results: T. versicolor presented a high growth rate (7.5 mm/day) on PDA. Submerged fermentations showed that T. versicolor assimilated lactose; however a slower consumption rate was observed in agitated cultures, compared to static cultures. The highest biomass production of 26 g/L was achieved in the CW-based medium, showing a protein content of 19.8%. Enrichment of whey protein films by T. versicolor biomass presented lower water vapor permeability and higher antioxidant capacity, compared to control films. Conclusion: The development of a novel CW biorefinery scheme was shown in this study, employing medicinal mushrooms for biomass production to create added-value food products towards a zero-food waste strategy. Graphical Abstract: [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer Nature B.V

Formulation of fermentation media from flour-rich waste streams for microbial lipid production by Lipomyces starkeyi

Flour-rich waste (FRW) and by-product streams generated by bakery, confectionery and wheat milling plants could be employed as the sole raw materials for generic fermentation media production, suitable for microbial oil synthesis. Wheat milling by-products were used in solid state fermentations (SSF) of Aspergillus awamori for the production of crude enzymes, mainly glucoamylase and protease. Enzyme-rich SSF solids were subsequently employed for hydrolysis of FRW streams into nutrient-rich fermentation media. Batch hydrolytic experiments using FRW concentrations up to 205 g/L resulted in higher than 90%(w/w) starch to glucose conversion yields and 40% (w/w) total Kjeldahl nitrogen to free amino nitro-gen conversion yields. Starch to glucose conversion yields of 98.2, 86.1 and 73.4% (w/w) were achieved when initial FRW concentrations of 235, 300 and 350 g/L were employed in fed-batch hydrolytic experiments, respectively. Crude hydrolysates were used as fermentation media in shake flask cultures with the oleaginous yeast Lipomyces starkeyi DSM 70296 reaching a total dry weight of 30.5 g/L with a microbial oil content of 40.4% (w/w), higher than that achieved in synthetic media. Fed-batch bioreactor cultures led to a total dry weight of 109.8 g/L with a microbial oil content of 57.8% (w/w) and productivity of 0.4 g/L/h