Fermented foods play a significant role in the diets of many cultures, and fermentation has been recognized for its many health benefits. During fermentation, the physical and biochemical changes due to microorganisms are crucial to the long-term stability of fermented foods. Recently, fermented foods have attracted the attention of scientists all over the world. Some putative mechanisms that explain how fermented foods affect health are the potential probiotic effects of the microorganisms in fermented foods, bioactive peptides and biogenic amines produced as a result of fermentation, phenolic compounds transformed to bioactive substances, and decreased antinutrients. In addition, increased vitamin content, antioxidant, antihypertensive, and antidiabetic activities have associated with fermented products. The purpose of this paper is to present various types of fermented foods and the health-promoting components that emerge during the fermentation of major food matrices, as well as the affect of fermented foods on the gut microbiome once they are ingested.

This study aimed to improve lipid and gamma-linolenic acid (GLA) production of an oleaginous fungus, Mucor plumbeus, through coculturing with Bacillus subtilis bacteria, optimising the environmental and nutritional culture conditions, and scaling them for batch fermentation. The maximum levels of biomass, lipid, fatty acid, and GLA in a 5 L bioreactor containing cellobiose and ammonium sulfate as the optimal carbon and nitrogen sources, respectively, achieved during the coculturing processes were 14.5 ± 0.4 g/L, 41.5 ± 1.3, 24 ± 0.8, and 20 ± 0.5%, respectively. This strategy uses cellobiose in place of glucose, decreasing production costs. The nutritional and abiotic factor results suggest that the highest production efficiency is achieved at 6.5 pH, 30 °C temperature, 10% (v/v) inoculum composition, 200 rpm agitation speed, and a 5-day incubation period. Interestingly, the GLA concentration of cocultures (20.0 ± 0.5%) was twofold higher than that of monocultures (8.27 ± 0.11%). More importantly, the GC chromatograms of cocultures indicated the presence of one additional peak corresponding to decanoic acid (5.32 ± 0.20%) that is absent in monocultures, indicating activation of silent gene clusters via cocultivation with bacteria. This study is the first to show that coculturing of Mucor plumbeus with Bacillus subtilis is a promising strategy with industrialisation potential for the production of GLA-rich microbial lipids and prospective biosynthesis of new products.

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Mucor circinelloides WJ11, an oleaginous filamentous fungus, produces 36% lipid of its cell dry weight when cultured in a high C/N ratio medium, however, the yield of γ-linolenic acid (GLA) is insufficient to make it competitive with other plant sources. To increase the GLA content in M. circinelloides WJ11, this fungus was engineered by overexpression of its key genes such as Δ6-, Δ12-, and Δ9-desaturases involved in GLA production. Firstly, we tried to overexpress two Δ6-desaturase isozymes to determine which one played important role in GLA synthesis. Secondly, Δ6-and Δ12-desaturase were co-overexpressed to check whether linoleic acid (LA), the precursor for GLA synthesis, is a limiting factor or not. Moreover, we tried to explore the effects of simultaneous overexpression of Δ6-, Δ12-, and Δ9-desaturases on GLA production. Our results showed that overexpression (1 gene) of DES61 promoted higher GLA content (21% of total fatty acids) while co-overexpressing (2 genes) DES61 and DES12 and simultaneous overexpressing (3 genes) DES61, DES12, and DES91 increased the GLA production of engineered strains by 1.5 folds and 1.9 folds compared to the control strain, respectively. This study provided more insights into GLA biosynthesis in oleaginous fungi and laid a foundation for further increase in GLA production into fungus such as M. circinelloides.

Malate transporter proteins (MTPs) play a pivotal role in regulating flux in the citrate/malate/pyruvate shuttle to deliver acetyl-CoA from the mitochondria to the cytosol and thus regulate lipid biosynthesis in oleaginous fungi. Despite the recent successful exploration of the mitochondrial malate transporters in Mucor circinelloides, research with in silico analyses that include molecular docking and their dynamics, in addition to homology modelling of malate transporters, have not been reported. In this study, the physico-chemical properties and nucleotide sequence analysis of two mitochondrial MTPs (MT and SoDIT-a with Gene/protein ID scafold00018.48 and scafold00239.15, respectively), in M. circinelloides WJ11 were performed. The three-dimensional (3D) model of the mitochondrial MTPs was determined and the best-docked complex stabilities were demonstrated with molecular dynamic (MD) simulations. The activity domain was revealed to form hydrogen bonds and piling interactions with citrate and malate upon docking. Our study showed better binding affinities for the MTPs—reaching up to −3.44 and −7.27 kcal/mol with the MT and SoDIT-a proteins, respectively (compared to the target of −2.85 and −6.00 kcal/mol for citric acid-binding). MD simulations illustrated that the protein complexes demonstrated conformational stability throughout the simulation. This study was the first to elucidate the structural characteristics of mitochondrial MTPs in M. circinelloides WJ11, providing direct evidence regarding the transport mechanism of specific substrates. Furthermore, the current results support ongoing efforts to combine functional and structural data to better understand the MTPs (at the molecular and atomic levels) of an oleaginous fungus such as M. circinelloides.