Integrated process for protein, pigments, and biogas production from baker's yeast wastewater using filamentous fungi

Resource recovery and valorization of food wastewater for sustainable development: An overview of current approaches

The food processing industry is one of the world's largest consumers of potable water. Agri-food wastewater systems consume about 70% of the world's fresh water and cause at least 80% of deforestation. Food wastewater is characterized by complex composition, a wide range of pollutants, and fluctuating water quality, which can cause huge environmental pollution problems if discharged directly. In recent years, food wastewater has attracted considerable attention as it is considered to have great prospects for resource recovery and reuse due to its rich residues of nutrients and low levels of harmful substances. This review explored and compared the sources and characteristics of different types of food wastewater and methods of wastewater treatment. Particular attention was paid to the different methods of resource recovery and reuse of food wastewater. The diversity of raw materials in the food industry leads to different compositional characteristics of wastewater, which determine the choice and efficiency of wastewater treatment methods. Physicochemical methods, and biological methods alone or in combination have been used for the efficient treatment of food wastewater. Current approaches for recycling and reuse of food wastewater include culture substrates, agricultural irrigation, and bio-organic fertilizers, recovery of high-value products such as proteins, lipids, biopolymers, and bioenergy to alleviate the energy crisis. Food wastewater is a promising substrate for resource recovery and reuse, and its valorization meets the current international policy requirements regarding food waste and environment protection, follows the development trend of the food industry, and is also conducive to energy conservation, emission reduction, and economic development. However, more innovative biotechnologies are necessary to advance the effectiveness of food wastewater treatment and the extent of resource recovery and valorization.

Effects of Red Yeast (Sporidiobolus pararoseus) on Growth, Innate Immunity, Expression of Immune-related Genes and Disease Resistance of Nile Tilapia (Oreochromis niloticus)

The purpose of this study was to evaluate the effects of red yeast (Sporidiobolus pararoseus) produced from crude glycerol, as a by-product of the biodiesel production process, on the growth, innate immunity, expression of immune-related gene, and resistance of Nile tilapia against challenge with Streptococcus agalactiae. Fish were fed diets supplied with different concentrations of S. pararoseus dried cells at 0.0 (control; T1), 5.0 (T2), 10.0 (T3), and 20.0 (T4) g kg-1 diets for 90 days. The results showed that final body weight, weight gain, and average daily gain were significantly higher in fish fed T3 and T4 compared to the control group (p < 0.05). Likewise, significant (p < 0.05) increases in total carotenoid content, liver superoxide dismutase activity (SOD), and serum lysozyme and albumin were observed in Nile tilapia fed S. pararoseus, with the highest (p < 0.05) values displayed in fish fed the T4 diet. Moreover, up-regulation of IL-1β transcription in Nile tilapia spleen and liver was observed in fish feeding group T4. In a challenge test against S. agalactiae, the fish survival rate was significantly higher in fish fed red yeast compared to the control group (p < 0.05). The highest bactericidal activity found in the T4 group (p < 0.05). However, no significant differences were found in hematology, blood chemical, malondialdehyde (MDA), body chemical composition, organosomatic indices, and myeloperoxidase (p > 0.05) in all treatments. The present results suggested that red yeast S. pararoseus (20.0 g kg-1) can be used as a potential supplementation on growth, immune response, and disease resistance of Nile tilapia.

Valorization of Baker Yeast Industry Waste in Agriculture by Improving Germination and Growth of Barley and Pea

Industrial waste still present an environmental danger for the nature and survival of all living beings. Among these toxic products, the focus has been on liquid effluents from the baker's yeast industry that cause real environmental problems mainly due to their pollutant load and the release of unpleasant odors. In order to minimize these hazards and to take advantage of these wastes for the sake of our environment, the present work consists on valorizing effluents from the baker's yeast industry on barley (Hordeum vulgare) and pea (Pisum sativum), two important agricultural products of Tunisian north-west. Results showed that this waste is characterized by its richness in organic matter, and the presence of proteins traces with high chemical and biochemical oxygen demand (COD and BOD5) values. Diluted effluent at a dose of 2.5 mg/g significantly improves germination of both plant seeds by germination index (GI) calculation, to reach a maximum of 190 ± 17% and 150 ± 14% for barley and pea, respectively. In fertigation experiment, the use of a lower dose of .62 mg/g of diluted effluent promotes plant length to reach 52 ± 4 cm and 45 ± 1.4 cm, respectively, for H. vulgare and P. sativum. Gas chromatography coupled to mass spectrometry (GC-MS) analysis after derivatization showed significant enhancement of auxin production in pea treated with .62 mg/g of cream compared to control with a concentration of 10.60 ± .81 and 8.16 ± .43 ng/gFW, respectively. In another experiment, the irrigation of pea plants with furfural, as major compound of cream, promotes length and auxin production to reach 9.89 ± .56 ng/gFW for a furfural dose of .31 mg/g. This leads us to valorize baker's yeast effluent as an environment-friendly natural product in pea and barley agricultural and give insight to its mode of action.

Light and oxygen facilitating the directly treatment food wastewater and poly-β-hydroxybutyrate, 5-aminolevulinic acid, pigment productions by Rubrivivax gelatinosus

Rubrivivax gelatinosus has the advantage of using wastewater to realize biomass recovery. However, they still cannot be applied large scale because they cannot directly treat the wastewater containing macromolecular organics. Thus, this article investigated the effects of light-oxygen conditions on R. gelatinosus by directly recycling wastewater containing macromolecular organics to produce biomass, poly-β-hydroxybutyrate (PHB), 5-aminolevulinic acid (5-ALA), and pigment. Results showed that R. gelatinosus directly treated the macromolecule organic (soybean protein and starch) wastewaters and achieved biomass recovery under light-anaerobic and light-micro-oxygen in six conditions. Chemical oxygen demand, protein, and starch removals for two wastewaters all reached above 70%. Renewable bio-resources such as biomass, PHB, 5-ALA, and pigment production were 10 times the initial content. Theoretical analysis indicated that light activated the synthesis of protease and amylase. However, oxygen concentration decided the number of enzymes. When oxygen was at micro-oxygen or anaerobic, the aforementioned expression and synthesis were conducted. In summary, this study expanded the viewpoint ignored by traditional theory. It was realized that R. gelatinosus directly treated wastewater and accumulated nutrients (biomass, PHB, pigment, and 5-ALA) for recycling, which reduced the secondary pollution of excess sludge into the environment.

Filamentous fungi for sustainable vegan food production systems within a circular economy: Present status and future prospects

Filamentous fungi serve as potential candidates in the production of different value-added products. In the context of food, there are several advantages of using filamentous fungi for food. Among the main advantages is that the fungal biomass used food not only meets basic nutritional requirements but that it is also rich in protein, low in fat, and free of cholesterol. This speaks to the potential of filamentous fungi in the production of food that can substitute animal-derived protein sources such as meat. Moreover, life-cycle analyses and techno-economic analyses reveal that fungal proteins perform better than animal-derived proteins in terms of land use efficiency as well as global warming. The present article provides an overview of the potential of filamentous fungi as a source of food and food supplements. The commercialization potential as well as social, legal and safety issues of fungi-based food products are discussed.

Enhancement of PHA Production by a Mixed Microbial Culture Using VFA Obtained from the Fermentation of Wastewater from Yeast Industry

Wastewater from the yeast production industry (WWY) is potentially harmful to surface water due to its high nitrogen and organic matter content; it can be used to produce compounds of higher commercial value, such as polyhydroxyalkanoates (PHA). PHA are polyester-type biopolymers synthesized by bacteria as energy reservoirs that can potentially substitute petrochemical-derived plastics. In this exploratory work, effluent from WWY was used to produce PHA, using a three-step setup of mixed microbial cultures involving one anaerobic and two aerobic reactors. First, volatile fatty acids (VFA; 2.5 g/L) were produced on an anaerobic batch reactor (reactor A) fed with WWY, using a heat pretreated sludge inoculum to eliminate methanogenic activity. Concurrently, PHA-producing bacteria were enriched using synthetic VFA in a sequencing batch reactor (SBR, reactor C) operated for 78 days. Finally, a polyhydroxybutyrate (PHB)-producing reactor (reactor B) was assembled using the inoculum enriched with PHA-producing bacteria and the raw and distilled effluent from the anaerobic reactor as a substrate. A maximum accumulation of 17% of PHB based on cell dry weight was achieved with a yield of 1.2 g PHB/L when feeding with the distilled effluent. Roche 454 16S rRNA gene amplicon pyrosequencing of the PHA-producing reactor showed that the microbial community was dominated by the PHA-producing bacterial species Paracoccus alcalophilus (32%) and Azoarcus sp. (44%). Our results show promising PHB accumulation rates that outperform previously reported results obtained with real substrates and mixed cultures, demonstrating a sustainable approach for the production of PHA less prone to contamination than a pure culture.