Simultaneous production of single cell protein and killer toxin by Wickerhamomyces anomalus HN1-2 isolated from mangrove ecosystem

Fungal deterioration of the bagasse storage from the harvested sugarcane

BACKGROUND

Sugarcane is an essential crop for sugar and ethanol production. Immediate processing of sugarcane is necessary after harvested because of rapid sucrose losses and deterioration of stalks. This study was conducted to fill the knowledge gap regarding the exploration of fungal communities in harvested deteriorating sugarcane. Experiments were performed on simulating production at 30 °C and 40 °C after 0, 12, and 60 h of sugarcane harvesting and powder-processing.

RESULTS

Both pH and sucrose content declined significantly within 12 h. Fungal taxa were unraveled using ITS amplicon sequencing. With the increasing temperature, the diversity of the fungal community decreased over time. The fungal community structure significantly changed within 12 h of bagasse storage. Before stored, the dominant genus (species) in bagasse was Wickerhamomyces (W. anomalus). Following storage, Kazachstania (K. humilis) and Saccharomyces (S. cerevisiae) gradually grew, becoming abundant fungi at 30 °C and 40 °C. The bagasse at different temperatures had a similar pattern after storage for the same intervals, indicating that the temperature was the primary cause for the variation of core features. Moreover, most of the top fungal genera were significantly correlated with environmental factors (pH and sucrose of sugarcane, storage time, and temperature). In addition, the impact of dominant fungal species isolated from the deteriorating sugarcane on sucrose content and pH in the stored sugarcane juice was verified.

CONCLUSIONS

The study highlighted the importance of timeliness to refine sugar as soon as possible after harvesting the sugarcane. The lessons learned from this research are vital for sugarcane growers and the sugar industry for minimizing post-harvest losses.

Fungi in mangrove ecosystems and their potential applications

Mangrove fungi, their ecological role in mangrove ecosystems, their bioproducts, and potential applications are reviewed in this article. Mangrove ecosystems can play an important role in beach protection, accretion promotion, and sheltering coastlines and creeks as barriers against devastating tropical storms and waves, seawater, and air pollution. The ecosystems are characterized by high average and constant temperatures, high salinity, strong winds, and anaerobic muddy soil. The mangrove ecosystems also provide the unique habitats for the colonization of fungi which can produce different kinds of enzymes for industrial uses, recycling of plants and animals in the ecosystems, and the degradation of pollutants. Many mangrove ecosystem-associated fungi also can produce exopolysaccharides, Ca²⁺-gluconic acid, polymalate, liamocin, polyunsaturated fatty acids, biofuels, xylitol, enzymes, and bioactive substances, which have many potential applications in the bioenergy, food, agricultural, and pharmaceutical industries. Therefore, mangrove ecosystems are rich bioresources for bioindustries and ecology. It is necessary to identify more mangrove fungi and genetically edit them to produce a distinct array of novel chemical entities, enzymes, and bioactive substances.

Yeast Mycocins: a great potential for application in health

Mycocins have demonstrated inhibition of fungi, bacteria, parasites and viruses, in addition to being studied as epidemiological markers and in the development of vaccines. They are defined as extracellular proteins or glycoproteins with different activities, the main mechanism of action being the inhibition of β-glucan synthesis in the cell wall of sensitive strains. Given the resistance problems created by several microorganisms to agents commonly used in clinical practice, the discovery of new substances with this purpose becomes essential. Mycocins have potential as anti-microbials because they show minimal toxicity and do not present resistance.

Production of a novel killer toxin from Saccharomyces eubayanus using agro-industrial waste and its application against wine spoilage yeasts

The juicing industry generates large amounts of waste that mostly lack commercial value and, in the absence of waste treatment policies, produces environmental pollution. Also, microbiological spoilage is a major concern in the wine industry and control tools are limited. Taking these challenges into account, agro-industrial waste coming from ultrafiltrated apple and pear juice were used to grow Saccharomyces eubayanus and to produce its killer toxin (SeKT). A Plackett-Burman screening was performed in order to optimize SeKT production in ultrafiltrated apple and pear juice. The optimized medium was characterized: 75% v/v WUJ, 0.5% m/v KH₂PO₄, 0.5% m/v MgSO₄, 0.5% m/v (NH₄)SO₄, 0.5% g/L urea, 10% v/v glycerol and 0.1% v/v Triton X-100. SeKT produced in WUJ optimised medium was used to perform killer assays against wine spoilage yeasts and showed antagonistic activity against Brettanomyces bruxellensis, Pichia guilliermondii, Pichia manshurica and Pichia membranifaciens. Different inhibition percentages against spoilage species in a wine environment (49-69%) were detected and preserved for at least 48 h. For the first time, this work reports the ability of S. eubayanus to produce a killer toxin with potential use as a biocontrol tool in winemaking. Producing SeKT using agro-industrial waste as an alternative medium to cultivate S. eubayanus would have industrial, economic and ecological benefits.

Bio-products produced by marine yeasts and their potential applications

It has been well documented that the yeasts isolated from different marine environments are so versatile that they can produce various fine chemicals, enzymes, bioactive substances, single cell protein and nanoparticles. Many genes related to the biosynthesis and regulation of these functional biomolecules have been cloned, expressed and characterized. All these functional biomolecules have a variety of applications in industries of food, chemical, agricultural, biofuel, cosmetics and pharmacy. In this review, a summary will be given about these functional biomolecules and their producers of the marine yeasts as well as some related genes in order to draw an outline about necessity for further exploitation of marine yeasts and their bio-products for industrial applications.

A novel killer toxin produced by the marine-derived yeast Wickerhamomyces anomalus YF07b

In our previous study, it was found that the killer toxin produced by the marine-derived yeast Wickerhamomyces anomalus YF07b has both killing activity and β-1,3-glucanase activity and the molecular mass of it is 47.0 kDa. In this study, the same yeast strain was found to produce another killer toxin which only had killing activity against some yeast strains, but had no β-1,3-glucanase activity and the molecular mass of the purified killer toxin was 67.0 kDa. The optimal pH, temperature and NaCl concentration for action of the purified killer toxin were 3.5, 16 °C and 4.0 % (w/v), respectively. The purified killer toxin could be bound by the whole sensitive yeast cells, but was not bound by manann, chitin and β-1,3-glucan. The purified killer toxin had killing activity against Yarrowia lipolytica, Saccharomyces cerevisiae, Metschnikowia bicuspidata WCY, Candida tropicalis, Candida albicans and Kluyveromyces aestuartii. Lethality of the sensitive cells treated by the newly purified killer toxin from W. anomalus YF07b involved disruption of cellular integrity by permeabilizing cytoplasmic membrane function.