Isolation and identification of Zalaria sp. Him3 as a novel fructooligosaccharides-producing yeast

Recent developments in the production of prebiotic fructooligosaccharides using fungal fructosyltransferases

Prebiotic nutritional ingredients have received attention due to their health-promoting potential and related uses in the food and nutraceutical industries. Recent times have witnessed an increasing interest in the use of fructooligosaccharides (FOS) as prebiotics and their generation using microbial enzymes. FOS consumption is known to confer health benefits such as protection against colon cancer, improved mineral absorption, lowering effect on serum lipid and cholesterol concentration, antioxidant properties, favourable dietary modulation of the human colonic microbiota, and immuno-modulatory effects. Comparative analysis of molecular models of various fructosyltransferases (FTases) reveals the mechanism of action and interaction of substrate with the active site. Microbial FTases carry out transfructosylation of sucrose into fructooligosaccharides (kestose, nystose, and fructofuranosylnystose), the most predominantly used prebiotic oligosaccharides. Furthermore, FOS has also been used for other purposes, such as low-calorie sweeteners, dietary fibres, and as the substrates for fermentation. This review highlights the occurrence, characteristics, immobilisation, and potential applications of FOS-generating fungal FTases. Production, heterologous expression, molecular characteristics, and modelling of fungal FTases underpinning their biotechnological prospects are also discussed.

Effects of fungal based bioactive compounds on human health: Review paper

Since the first years of history, microbial fermentation products such as bread, wine, yogurt and vinegar have always been noteworthy regarding their nutritional and health effects. Similarly, mushrooms have been a valuable food product in point of both nutrition and medicine due to their rich chemical components. Alternatively, filamentous fungi, which can be easier to produce, play an active role in the synthesis of some bioactive compounds, which are also important for health, as well as being rich in protein content. Therefore, this review presents some important bioactive compounds (bioactive peptides, chitin/chitosan, β-glucan, gamma-aminobutyric acid, L-carnitine, ergosterol and fructooligosaccharides) synthesized by fungal strains and their health benefits. In addition, potential probiotic- and prebiotic fungi were researched to determine their effects on gut microbiota. The current uses of fungal based bioactive compounds for cancer treatment were also discussed. The use of fungal strains in the food industry, especially to develop innovative food production, has been seen as promising microorganisms in obtaining healthy and nutritious food.

De novo genome assembly and analysis of Zalaria sp. Him3, a novel fructooligosaccharides producing yeast

Background

Zalaria sp. Him3 was reported as a novel fructooligosaccharides (FOS) producing yeast. However, Zalaria spp. have not been widely known and have been erroneously classified as a different black yeast, Aureobasidium pullulans. In this study, de novo genome assembly and analysis of Zalaria sp. Him3 was demonstrated to confirm the existence of a potential enzyme that facilitates FOS production and to compare with the genome of A. pullulans.

Results

The genome of Zalaria sp. Him3 was analyzed; the total read bases and total number of reads were 6.38 Gbp and 42,452,134 reads, respectively. The assembled genome sequence was calculated to be 22.38 Mbp, with 207 contigs, N50 of 885,387, L50 of 10, GC content of 53.8%, and 7,496 genes. g2419, g3120, and g3700 among the predicted genes were annotated as cellulase, xylanase, and β-fructofuranosidase (FFase), respectively. When the read sequences were mapped to A. pullulans EXF-150 genome as a reference, a small amount of reads (3.89%) corresponded to the reference genome. Phylogenetic tree analysis, which was based on the conserved sequence set consisting of 2,362 orthologs in the genome, indicated genetic differences between Zalaria sp. Him3 and Aureobasidium spp.

Conclusion

The differences between Zalaria and Aureobasidium spp. were evident at the genome level. g3700 identified in the Zalaria sp. Him3 likely does not encode a highly transfructosyl FFase because the motif sequences were unlike those in other FFases involved in FOS production. Therefore, strain Him3 may produce another FFase. Furthermore, several genes with promising functions were identified and might elicit further interest in Zalaria yeast.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-022-01094-2.