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Compared with the traditional suspension fermentation, immobilised biofilm fermentation has advantages of strong resistance, high yield and continuous fermentation and is conducive to improving the industrial fermentation methods. The formation of a biofilm on correct supports is critical to immobilised fermentation. In this study, Pichia pastoris was used to understand and control the modification of surface properties of supports and cells. Following deletion of gene PAS_chr2-1_0773, in P. pastoris △0773, the cell-surface negative charge density decreased and hydrophobicity improved, which was conducive to adhesion. Therefore, according to the changing trend of cell surface properties, cotton fibre was used with succinic anhydride (SA) to modify the carrier for changing the surface properties for efficient conduction of immobilised fermentation. In the fermentation process, the adhesion between the modified cotton fibre and yeast was better than that between an unmodified cotton fibre and yeast, and the additive amount increased by ∼25 %. The enzyme activity of the △0773-cotton-SA fermentation system reached 302.7 U/mL, which was 39.6 % higher than that of the original fermentation system. Therefore, this study provides a guide for significant improvement of immobilised fermentation of fungi.

Biofilm-based fermentation, as a new immobilisation strategy, is beneficial for industrial fermentation due to its excellent environmental resistance, high productivity and continuous fermentation relative to calcium alginate-immobilised fermentation. These two techniques differ mainly regarding cell stages. Here, we describe the cell phenotype of Saccharomyces cerevisiae biofilm-based fermentation and compare cell cycle stages with those during immobilisation in calcium alginate. Most cells in the biofilm-based fermentation adhered to the cotton-fibre carrier of the biofilm and were in the G2/M phase whereas alginate-embedded cells were in the G1/G0 phase. Deletion of the RIM15 gene, which regulates cell cycle progression according to nutritional status, hampered the cell cycle arrest observed in alginate-embedded cells, enhanced biofilm formation and improved fermentation ability. The improved biofilm formation shown by the rim15△ strain could be attributed to an increase in the expression level of the adhesion protein FLO11 and synthesis of trehalose. These findings suggest that the extracellular environment is mainly responsible for the difference between biofilm-based fermentation and alginate-embedded fermentation, and that RIM15 plays an essential role in cell cycle progression. KEY POINTS: • In the biofilm, S. cerevisiae cell populations were mostly in the G2/M phase while alginate-embedded cells were arrested in the G1/G0 phase. • The RIM15 gene partially influenced the cell cycle progression observed during ethanol fermentation. • Biofilm-based cells were actively adsorbed on the physical carrier. • Biofilm immobilisation could maintain cell division activity explaining its fermentation efficiency.

Biofilms are a form of microbial community that can be beneficial for industrial fermentation because of their remarkable environmental resistance. However, the mechanism of biofilm formation in Saccharomyces cerevisiae remains to be fully explored, and this may enable improved industrial applications for this organism. Although quorum-sensing (QS) molecules are known to be involved in bacteria biofilm formation, few studies have been undertaken with these in fungi. 2-phenylethanol (2-PE) is considered a QS molecule in S. cerevisiae. Here, we found that exogenous 2-PE could stimulate biofilm formation at low cell concentrations. ARO8p and ARO9p are responsible for the synthesis of 2-PE and were crucial to the formation of biofilm. Deletion of the ARO8 and ARO9 genes reduced the content of 2-PE in the early stage of fermentation, reduced ethanol yield and decreased biofilm formation. The expression of FLOp, which is involved in cell adhesion, and the content of extracellular polysaccharides of mutant strains ΔARO8 and ΔARO9 were also significantly reduced. These findings indicate that the production of 2-PE had a positive effect on biofilm formation in S. cerevisiae, thereby providing further key details for studying the formation of biofilm mechanism in the future. KEY POINTS: • Quorum-sensing molecule 2-PE positively affects biofilm formation in S. cerevisiae. • 2-PE synthetic genes ARO8 and ARO9 deletion reduced extracellular polysaccharide. • ARO8 and ARO9 deletion reduced the gene expression of the FLO family.

Ophiocordyceps sinensis (syn. Cordyceps sinensis), well known as DongChongXiaCao (DCXC), is one of the most valuable traditional Chinese medicinal species. In this article, we provide a systematic review of natural enemies and diseases encountered in artificial cultivation of DCXC. Unfortunately, DCXC has been endangered over the past decades due to overharvesting and a worsening ecological environment. Therefore, the artificial cultivation of DCXC has been extensively investigated in recent years. Complete indoor artificial cultivation and semi-field cultivation are the two most common strategies used to cultivate DCXC. However, cultured DCXCs are often attacked by various natural enemies and diseases, which have resulted in substantial loss of the valuable medicinal resource. In this study, we have summarized the species of natural enemies and types of diseases confronted by DCXC. Twenty reported natural enemy species are categorized into four classes, one of which is reported for the first time in this study. Moreover, six microbial pathogens are also discussed. The recapitulation of the natural enemies and diseases in DCXC artificial cultivation not only promote the development of integrated pest management of DCXC cultivation but also provide important information to help preserve and develop this valuable resource.

Although Hepialus xiaojinensis is important as the host of Ophiocordyceps sinensis, it remains poorly known especially in genetic structure and phylogeny status. To get a better understanding of it, the complete mitochondrial genome sequence of H. xiaojinensis was sequenced for the first time. The genome was 15 397 bp in size and contained 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and an AT-rich region, and the gene composition and the arrangement of which were consistent with other insects of Hepialidae. The base composition of the genome was A (41.44%), T (39.68%), C (11.52%), and G (7.36%), with an AT content of 81.13%. Moreover, we have performed phylogenetic analysis of H. xiaojinensis and other 11 Lepidoptera species.

Background Atrial fibrillation (AF) is characterized by structural remodeling, contractile dysfunction, and AF progression. Histone deacetylases (HDACs) influence acetylation of both histones and cytosolic proteins, thereby mediating epigenetic regulation and influencing cell proteostasis. Because the exact function of HDACs in AF is unknown, we investigated their role in experimental and clinical AF models.

Surface electrocardiogram (ECG), sinus node electrogram (SNE), His bundle electrogram (HBE), and intracardiac electrogram of high right atrium (HRA) were recorded synchronously in 11 of the 14 consecutive cases with complete atrioventricular block (CAVB). SNE showed the presence of a pre-P wave that preceded in all the P wave on the ECG and had no relationship to QRS complex or TU repolarization. This confirmed that the pre-P wave arose from the sinus node. Direct sinoatrial conduction time (SACTd) in nine cases was within the normal range (less than 120 msec). SACTd in another two cases was prolonged to 185 msec and 210 msec, respectively, suggesting their abnormal sinus node conduction.

We recommend a technique for recording a sinus node electrogram (SNE) that is quite simple and makes it easy to locate the electrode poles firmly in the place underlying the sinus node (SN); the success rate is 97%.