Improvement of laccase activity by silencing PacC in Ganoderma lucidum

Identification of Novel Laccase from Ganoderma lucidum and Application in Biotransformation to Bio-based Fragrances Using Alkaline Lignin as Raw Material

A novel laccase, Lac3, was purified from Ganoderma lucidum fermentation broth by salting out, gel filtration chromatography, and Native-PAGE protein recovery. The molecular mass of Lac3 was 58.4 kDa as estimated by SDS-PAGE and exhibited catalytic properties with 2,2'-Biazobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) as substrate. The specific enzyme activity of Lac3 was determined to be 313.69 U/mg. The laccase was stable at temperatures < 65 °C and at pH of 2.5-4.5. The pH, temperature optima, Km and Vmax of the enzyme for ABTS oxidation were 3.0, 55 °C, 0.077 mM, and 2.98 mM/min, respectively. The metal ions and anions showed inhibitory effects on Lac3 activity except Cu2+ (1 mM). GC-MS analysis showed that various aroma products were generated by Lac3 treatment of alkaline lignin. The Lac3 and lignin model compounds had negative binding energy and hydrogen bonding. The analysis of docking suggested that Asp207, Asn256, and His459 play a key role in substrate binding and catalysis.

Alternative splicing of Gllac7 regulate lignin degradation in Ganoderma lucidum

Laccases are key enzymes involved in lignin degradation in the white-rot fungus Ganoderma lucidum. Gllac7, which exists as two alternative splice isoforms, Gllac7.1 and Gllac7.2, plays a significant role in the lignin degradation process in G. lucidum. In this study, we examined the functions of the two isoforms and explored the transcriptional regulation mechanism of Gllac7.1. On lignin medium (LM), the expression of Gllac7.1 was 25.11-fold higher than on glucose medium (MM), whereas the expression of Gllac7.2 was 0.62-fold lower than that of MM. On MM, the OE/RNAi_Gllac7.1 and OE/RNAi_Gllac7.2 transformants exhibited no phenotypic differences from the wild-type (WT) strain. However, on LM, the OE_Gllac7.1 and RNAi_Gllac7.2 transformants exhibited accelerated growth and enhanced lignin degradation rates, reaching 1.28 to 2.04 times those of the WT. Moreover, RNAi_Gllac7.2 transformants formed primordia two to three days earlier than that of the WT. A C2H2 zinc finger protein, chr8g0158731, can bind to the promoter of Gllac7.1. Furthermore, RNAi_chr8g0158731 transformants displayed increased expression of Gllac7.1 and demonstrated improved bagasse degradation capabilities. These findings provide valuable insights into the roles of alternative splice isoforms of G. lucidum laccase, offering a foundation for future molecular marker-assisted breeding efforts.

Ganoderma lucidum driven fermentation of Rosa roxburghii pomace: Effects on noodle physicochemical properties, digestion, and gut microbiota

Rosa roxburghii pomace (RRP) is a high dietary fiber byproduct that is underutilized. This study investigated the effects of Ganoderma lucidum fermented Rosa roxburghii pomace (FRRP) on noodle cooking characteristics, texture, structure, in vitro digestion, and fermentation. The results showed that soluble dietary fiber, active components (polysaccharides, triterpenoids and dietary flavonoids), and the total cellulase (Filter paper enzymes, Carboxymethyl cellulase), β-glucosidase and laccase activity were significantly increased in FRRP (p < 0.05). FRRP improved the cooking and sensory properties of noodles and inhibited starch hydrolysis during in vitro digestion. The resistant starch content in noodles with 15 % FRRP increased by 12.63 %, and the predicted glycemic index decreased by 9.34 %. Moreover, the intestinal microbiota structure was significantly improved, promoting the growth of beneficial bacteria such as Bifidobacterium and Lactobacillus. This study contributed to the high-value and environmentally friendly utilization of RRP and provided new insights into the development of efficient noodles.

Transcription factors: switches for regulating growth and development in macrofungi

Macrofungi (or mushrooms) act as an extraordinarily important part to human health due to their nutritional and/or medicinal value, but the detailed researches in growth and development mechanisms have yet to be explored further. Transcription factors (TFs) play indispensable roles in signal transduction and affect growth, development, and metabolism of macrofungi. In recent years, increasing research effort has been employed to probe the relationship between the development of macrofungi and TFs. Herein, the present review comprehensively summarized the functional TFs researched in macrofungi, including modulating mycelial growth, fructification, sclerotial formation, sexual reproduction, spore formation, and secondary metabolism. Meanwhile, the possible effect mechanisms of TFs on the growth and development of some macrofungi were also revealed. Specific examples of functional characterizations of TFs in macrofungi (such as Schizophyllum commune and Coprinopsis cinerea) were described to a better comprehension of regulatory effect. Future research prospects in the field of TFs of macrofungi are discussed. We illustrated the functional versatility of the TFs in macrofungi based on specific examples. A systematical realization of the interaction and possible mechanisms between TFs and macrofungi can supply possible solutions to regulate genetic characteristics, which supply novel insights into the regulation of growth, development and metabolism of macrofungi. KEY POINTS: • The functional TFs researched in macrofungi were summarized. • The possible effect mechanisms of TFs in macrofungal were described. • The multiple physiological functions of TFs in macrofungi were discussed.

Gllac7 Is Induced by Agricultural and Forestry Residues and Exhibits Allelic Expression Bias in Ganoderma lucidum

Ganoderma lucidum has a wide carbon spectrum, while the expression profile of key genes relevant to carbon metabolism on different carbon sources has been seldom studied. Here, the transcriptomes of G. lucidum mycelia cultured on each of 19 carbon sources were conducted. In comparison with glucose, 16 to 1,006 genes were upregulated and 7 to 1,865 genes were downregulated. Significant gene expression dynamics and induced activity were observed in laccase genes when using agricultural and forestry residues (AFRs) as solo carbon sources. Furthermore, study of laccase gene family in two haploids of G. lucidum GL0102 was conducted. Totally, 15 and 16 laccase genes were identified in GL0102_53 and GL0102_8, respectively, among which 15 pairs were allelic genes. Gene structures were conserved between allelic laccase genes, while sequence variations (most were SNPs) existed. Nine laccase genes rarely expressed on all the tested carbon sources, while the other seven genes showed high expression level on AFRs, especially Gllac2 and Gllac7, which showed 5- to 1,149-fold and 4- to 94-fold upregulation in mycelia cultured for 5 days, respectively. The expression of H53lac7 was consistently higher than that of H8lac7_1 on all the carbon sources except XM, exhibiting a case of allelic expression bias. A total of 47 SNPs and 3 insertions/deletions were observed between promoters of H53lac7 and H8lac7_1, which lead to differences in predicted binding sites of zinc fingers. These results provide scientific data for understanding the gene expression profile and regulatory role on different carbon sources and may support further functional research of laccase.

Laccases and Tyrosinases in Organic Synthesis

Laccases (Lac) and tyrosinases (TYR) are mild oxidants with a great potential in research and industry. In this work, we review recent advances in their use in organic synthesis. We summarize recent examples of Lac-catalyzed oxidation, homocoupling and heterocoupling, and TYR-catalyzed ortho-hydroxylation of phenols. We highlight the combination of Lac and TYR with other enzymes or chemical catalysts. We also point out the biological and pharmaceutical potential of the products, such as dimers of piceid, lignols, isorhamnetin, rutin, caffeic acid, 4-hydroxychalcones, thiols, hybrid antibiotics, benzimidazoles, benzothiazoles, pyrimidine derivatives, hydroxytyrosols, alkylcatechols, halocatechols, or dihydrocaffeoyl esters, etc. These products include radical scavengers; antibacterial, antiviral, and antitumor compounds; and building blocks for bioactive compounds and drugs. We summarize the available enzyme sources and discuss the scalability of their use in organic synthesis. In conclusion, we assume that the intensive use of laccases and tyrosinases in organic synthesis will yield new bioactive compounds and, in the long-term, reduce the environmental impact of industrial organic chemistry.