Optimisation of α-terpineol production by limonene biotransformation using Penicillium digitatum DSM 62840

Transcription Factor PdTP1 Regulates the Biotransformation of Limonene to α-Terpineol and the Growth of Penicillium digitatum

α-Terpineol, an alcoholic monoterpene with lilac-like aroma, possesses diverse biological activities and has found applications in the food, pharmaceutical, cosmetic, and agricultural industries. Our previous studies indicated that gene PdTP1 was highly expressed in Penicillium digitatum DSM 62840 during the biotransformation of limonene to α-terpineol, while its actual biological functions are not fully understood. Here, PdTP1 was functionally characterized with bioinformatics analysis, subcellular localization, transcriptional activation activity, overexpression, and RNA interference (RNAi) silencing and RNA-seq analysis. Results showed that PdTP1 protein contained a GAL4-like Zn2Cys6 DNA-binding domain and a fungal_trans domain, was located in the nucleus and cell membrane and presented transcriptional activation effect, suggesting that PdTP1 encoded a Zn2Cys6 type transcription factor. Overexpression of PdTP1 in P. digitatum promoted limonene biotransformation and increased α-terpineol production, and opposite results were observed after the silencing of PdTP1. Moreover, transcription factor PdTP1 was found to affect the growth of P. digitatum and participate in ionic stress and oxidative stress responses. RNA-seq data revealed that altering the PdTP1 expression influenced the expression of some genes related to terpene metabolism or biosynthesis, fungal growth, and stress responses. In summary, PdTP1, which encoded a Zn2Cys6 transcription factor, played important roles in improving the production of α-terpineol from limonene and regulating fungal growth and environmental stress responses.

Transcriptomic analysis of Sitophilus zeamais in response to limonene fumigation

BACKGROUND

Frequent application of chemical fumigants has contributed to the development of resistance in stored-product pests. Essential oils provide a novel and environmentally friendly alternative to conventional chemical pesticides. In this work, the fumigant activity of Taxodium 'zhongshansha' essential oil (TZEO) and main active components against Sitophilus zeamais were evaluated. In addition, the molecular mechanisms mediating the fumigant activity of limonene were assessed.

RESULTS

TZEO showed strong fumigant activity against Sitophilus zeamais, with a 50% lethal concentration (LC₅₀ ) of 22.90 μL L^-1 air in 24 h. The main components of TZEO were identified using gas chromatography-mass spectrometry, the main active ingredient (limonene) showed an LC₅₀ of 9.93 μL L^-1 air in 24 h which had a serious dose-time-effect. The LC₅₀ value of the positive control (aluminum phosphide) was 1.91 μL L^-1 . In total, 3982 up-regulated and 3067 down-regulated genes were sequenced in limonene-fumigated Sitophilus zeamais, the genes related to metabolic detoxification were significantly enriched. The mortality rate of 7 day-old Sitophilus zeamais adult mediated with knockdown of SzCYP6MS5 and SzCYP6MS6 raised up to 65.67% and 67.65% after fumigation with limonene in 24 h, respectively. The results showed that SzCYP6MS5 and SzCYP6MS6 are closely involved to the detoxification of limonene.

CONCLUSION

In this study, candidate genes affected by limonene treatment in Sitophilus zeamais were identified. These findings provided insights into the systemic metabolic response of Sitophilus zeamais to limonene and established a basis for the development of limonene as a botanical pesticide for the control of stored-product pests. © 2022 Society of Chemical Industry.

An update on the progress of microbial biotransformation of commercial monoterpenes

Monoterpenes, a class of isoprenoid compounds, are extensively used in flavor, fragrance, perfumery, and cosmetics. They display many astonishing bioactive properties of biological and pharmacological significance. All monoterpenes are derived from universal precursor geranyl diphosphate. The demand for new monoterpenoids has been increasing in flavor, fragrances, perfumery, and pharmaceuticals. Chemical methods, which are harmful for human and the environment, synthesize most of these products. Over the years, researchers have developed alternative methods for the production of newer monoterpenoids. Microbial biotransformation is one of them, which relied on microbes and their enzymes. It has produced many new desirable commercially important monoterpenoids. A growing number of reports reflect an ever-expanding scope of microbial biotransformation in food and aroma industries. Simultaneously, our knowledge of the enzymology of monoterpene biosynthetic pathways has been increasing, which facilitated the biotransformation of monoterpenes. In this article, we have covered the progress made on microbial biotransformation of commercial monoterpenes with a brief introduction to their biosynthesis. We have collected several reports from authentic web sources, including Google Scholar, Pubmed, Web of Science, and Scopus published in the past few years to extract information on the topic.

A Comparative Study on Relieving Exercise-Induced Fatigue by Inhalation of Different Citrus Essential Oils

Citrus essential oils (CEOs) possess physiological functions due to diverse aroma components. However, evidence for the effects of CEOs on exercise performance and exercise-induced fatigue is limited. The CEOs with discrepancies in components may exert different effects on the amelioration of exercise-induced fatigue. In this study, sweet orange (Citrus sinensis L.) essential oil (SEO), lemon (Citrus limon Osbeck) essential oil (LEO), and bergamot (Citrus bergamia Risso and Poit) essential oil (BEO) were chosen to explore the effect on amelioration of exercise-induced fatigue. Our results demonstrated that SEO and LEO increased the swimming time by 276% and 46.5%, while BEO did not. Moreover, the three CEOs exerted varying effects on mitigating exercise-induced fatigue via inhibiting oxidative stress, protecting muscle injury, and promoting glucose-dependent energy supply. Accordingly, BEO showed the best efficiency. Moreover, the GC-MS and Pearson correlation analysis of BEO showed that the contents of the major components, such as (±)-limonene (32.9%), linalyl butyrate (17.8%), and linalool (7.7%), were significantly positively correlated with relieving exercise-induced fatigue.

Microbial valorization of underutilized and nonconventional waste streams

The growing burden of waste disposal coupled with natural resource scarcity has renewed interest in the remediation, valorization, and/or repurposing of waste. Traditional approaches such as composting, anaerobic digestion, use in fertilizers or animal feed, or incineration for energy production extract very little value out of these waste streams. In contrast, waste valorization into fuels and other biochemicals via microbial fermentation is an area of growing interest. In this review, we discuss microbial valorization of nonconventional, aqueous waste streams such as food processing effluents, wastewater streams, and other industrial wastes. We categorize these waste streams as carbohydrate-rich food wastes, lipid-rich wastes, and other industrial wastes. Recent advances in microbial valorization of these nonconventional waste streams are highlighted, along with a discussion of the specific challenges and opportunities associated with impurities, nitrogen content, toxicity, and low productivity.

Advances on (+)-nootkatone microbial biosynthesis and its related enzymes

(+)-Nootkatone is an important functional sesquiterpene and is comprehensively used in pharmaceutical, cosmetic, agricultural and food flavor industries. However, (+)-nootkatone is accumulated trace amounts in plants, and the demand for industry is mainly met by chemical methods which is harmful to the environment. The oxygen-containing sesquiterpenes prepared using microbial methods can be considered as "natural." Microbial transformation has the advantages of mild reaction conditions, high efficiency, environmental protection, and strong stereoselectivity, and has become an important method for the production of natural spices. The microbial biosynthesis of (+)-nootkatone from the main precursor (+)-valencene is summarized in this paper. Whole-cell systems of fungi, bacteria, microalgae, and plant cells have been employed. It was described that the enzymes involved in the microbial biosynthesis of (+)-nootkatone, including cytochrome p450 enzymes, laccase, lipoxygenase, and so on. More recently, the related enzymes were expressed in microbial hosts to heterologous produce (+)-nootkatone, such as Escherichia coli, Pichia pastoris, Yarrowia lipolytica, and Saccharomyces cerevisiae. Finally, the development direction of research for realizing industrialization of microbial transformation was summarized and it provided many options for future improved bioprocesses.

Changes of fungal community and non-volatile metabolites during pile-fermentation of dark green tea

Fungal community and non-volatile metabolites changes during the pile-fermentation are key factors to organoleptic qualities of dark green tea. However, the correlation between fungal succession and non-volatile compounds has never been satisfactorily explained. The purpose of the present study was to investigate fungal succession and its correlation with flavor compounds by multi-omics. Illumina Miseq sequencing of ITS1 region was conducted to analyze the fungal succession, a total of 78 OTUs which consisted of one phyla, nine classes, 15 orders, 26 families, 37 genera were identified, with Ascomycota as dominant phyla. Cluster analysis and non-metric multidimensional scaling of samples demonstrated the distribution of OTUs in multi-dimensional space, the pile-fermentation process of dark green tea can be divided into four periods according to the generated trajectory of fungal population, S0, S1-S3, S4-S5, and S6. Aspergillus is the dominant genus. Penicillium, Cyberlindnera, Debaryomyces, Candida, Thermomyces, Rasamsonia, Thermoascus, and Byssochlamys appear in different periods. three alkaloids, seven catechins, nine amino acids, five organic acids, five flavones and flavonoid glycosides were identified by UPLC-QTOF-MS/MS, and the contents were all decreasing. Caffeine, EGC, EGCG, L-theanine, kaempferitrin, L-phenylalanine, gallic acid, and myricetin-3-O-galactoside are important ingredients which contribute to the flavor of dark green tea. This study demonstrated the fungal succession, non-volatile flavor compounds and their relationships during pile-fermentation of dark green tea, and provides new insights into evaluating pivotal role of fungal succession in the manufacturing process of dark green tea.

Screening a Strain of Klebsiella sp. O852 and the Optimization of Fermentation Conditions for Trans-Dihydrocarvone Production

Flavors and fragrances have high commercial value in the food, cosmetic, chemical and pharmaceutical industries. It is interesting to investigate the isolation and characterization of new microorganisms with the ability to produce flavor compounds. In this study, a new strain of Klebsiella sp. O852 (accession number CCTCC M2020509) was isolated from decayed navel orange (Citrus sinensis (L.) Osbeck), which was proved to be capable of converting limonene to trans-dihydrocarvone. Besides, the optimization of various reaction parameters to enhance the trans-dihydrocarvone production in shake flask was performed for Klebsiella sp. O852. The results showed that the yield of trans-dihydrocarvone reached up to 1 058 mg/L when Klebsiella sp. O852 was incubated using LB-M medium for 4 h at 36 °C and 150 rpm, and the biotransformation process was monitored for 36 h after adding 1680 mg/L limonene/ethanol (final ethanol concentration of 0.8% (v/v)). The content of trans-dihydrocarvone increased 16 times after optimization. This study provided a basis and reference for producing trans-dihydrocarvone by biotransformation.

Bioproduction of α-terpineol and R-(+)-limonene derivatives by terpene-tolerant ascomycete fungus as a potential contribution to the citrus value chain

AIMS

The aims of this article were to select fungal species with high tolerance and high growth rate in mediums supplemented with limonene and citrus essential oils (CEOs), and to test the bioconversion capability of the chosen isolates for the bioproduction of aroma compounds.

METHODS AND RESULTS

Based on the use of predictive mycology, 21 of 29 isolates were selected after assaying R-(+)-limonene and CEO tolerance (10 g l^-1 ). With a dendrogram divisive coefficient of 0·937, the subcluster two with isolates Aspergillus niger LBM 055, Penicillium sp. LBM 150, Penicillium sp. LBM 151 and Penicillium sp. LBM 154 gathered the highest tolerance and mycelia growth speed. Ultrastructural analysis indicated that culture media containing limonene had no visible toxic activity that could promote morphological changes in the fungal cell wall. The biomass of A. niger LBM055 was distinctive in liquid media supplemented with R-(+)-limonene (0·57 ± 0·07 g) and it was selected to prove bioconversion capacity, under static and agitated conditions, and converted up to 98% of limonene, yielding a wide variety of products that were quantified by GC-FID. It was obtained at molecular weights less than limonene (64-100%), between limonene and α-terpineol (12-72%) and greater than α-terpineol (2-48%).

CONCLUSIONS

Aspergillus niger LBM 055, Penicillium sp. LBM 150, Penicillium sp. LBM 151 and Penicillium sp. LBM 154 showed to the highest tolerance and growth rate in mediums supplemented with R-(+)-limonene and orange and lemon essential oils. Particularly, A. niger LBM055, showed limonene bioconversion capability and produced different molecular weights compounds such us α-terpineol.

SIGNIFICANCE AND IMPACT OF THE STUDY

Different bioproducts can be obtained by changing operative condition with the same fungus, and this bioprocess aspect is a significant approach to be adopted on industrial scale leading to the creation of new natural flavours and fragrance compositions.

Mutagenesis and Adaptation of the Psychrotrophic Fungus Chrysosporium pannorum A-1 as a Method for Improving β-pinene Bioconversion

Mutagenesis and adaptation of the psychrotrophic fungus Chrysosporium pannorum A-1 to the toxic substrate β-pinene were used to obtain a biocatalyst with increased resistance to this terpene and improved bioconversion properties. Mutants of the parental strain were induced with UV light and N-methyl-N'-nitro-N-nitrosoguanidine. Mutants resistant to β-pinene were isolated using agar plates with a linear gradient of substrate concentrations. Active mutants were selected based on their general metabolic activity (GMA) expressed as oxygen consumption rate. Compared to the parental strain, the most active mutant showed an enhanced biotransformation ability to convert β-pinene to trans-pinocarveol (315 mg per g of dry mycelium), a 4.3-fold greater biocatalytic activity, and a higher resistance to H2O2-induced oxidative stress. Biotransformation using adapted mutants yielded twice as much trans-pinocarveol as the reaction catalyzed by non-adapted mutants. The results indicate that mutagenesis and adaptation of C. pannorum A-1 is an effective method of enhancing β-bioconversion of terpenes.

Genomic and Transcriptomic Study for Screening Genes Involved in the Limonene Biotransformation of Penicillium digitatum DSM 62840

α-Terpineol has been widely used in daily chemical, pharmaceutical, food, and flavor industries due to its pleasant odor with high economic value and pharmacological action. Our previous study showed that Penicillium digitatum DSM 62840 was an efficient biocatalyst for the transformation of limonene to α-terpineol. Thus, it was meaningful to explore the genome features and the gene expression differences of strain DSM 62840 during limonene biotransformation, and the detailed bioconversion pathways. In this study, the functional genes related to limonene bioconversion were investigated using genome and transcriptome sequences analysis. The results showed that the P. digitatum DSM 62840 genome was estimated to be 29.09 Mb and it encoded 9,086 protein-encoding genes. The most annotated genes were associated to some protein metabolism and energy metabolism functions. When the threshold for differentially expressed genes (DEGs) was set at twofold ratio, a total of 4,128, and 4,148 DEGs were identified in P_L_12h (limonene-treated condition) compared with P_0h (blank) and P_12h (limonene-untreated blank), respectively. Among them, the expression levels of genes involved in the biosynthesis of secondary metabolites, energy metabolism and ATP-binding cassette (ABC) transporters were significantly altered during the biotransformation. And the reliability of these results was further confirmed by quantitative real-time polymerase chain reaction (RT-qPCR). Moreover, we found that the enzyme participated in limonene biotransformation was inducible. This enzyme was located in the microsome, and it was inhibited by cytochrome P450 inhibitors. This indicated that the cytochrome P450 may be responsible for the limonene bioconversion. Several differentially expressed cytochrome P450 genes were further identified, such as PDIDSM_85260 and PDIDSM_67430, which were significantly up-regulated with limonene treatment. These genes may be responsible for converting limonene to α-terpineol. Totally, the genomic and transcriptomic data could provide valuable information in the discovery of related-genes which was involved in limonene biotransformation, pathogenicity of fungi, and investigation of metabolites and biological pathways of strain DSM 62840.

Antidepressant-like Effect of Citrus sinensis (L.) Osbeck Essential Oil and Its Main Component Limonene on Mice

The present study investigated the antidepressant-like effects of navel orange [Citrus sinensis (L.) Osbeck] essential oil (OEO) and its main components using the chronic unpredictable mild stress (CUMS) model mice and explored its possible mechanisms. The results indicated that OEO inhalation significantly ameliorated the depression-like behaviors of CUMS mice with decreased body weight, sucrose preference, curiosity, and mobility as well as shortened immobile time and attenuated dyslipidemia. Limonene was the most abundant compound in the sniffing OEO environment and mice brain after sniffing, and it was not metabolized immediately in the brain. In addition, limonene inhalation significantly restored CUMS-induced depressive behavior, hyperactivity of hypothalamic-pituitary-adrenal axis, and the decrease of monoamine neurotransmitter levels, with downregulation of brain-derived neurotrophic factor and its receptor expression in the hippocampus. Thus, the study indicates that the improvements in neuroendocrine, neurotrophic, and monoaminergic systems are related to the antidepressant effects of limonene.

Proteins differentially expressed during limonene biotransformation by Penicillium digitatum DSM 62840 were examined using iTRAQ labeling coupled with 2D-LC–MS/MS

This study focused on the differences in protein expression at various periods during limonene biotransformation by Penicillium digitatum DSM 62840. A total of 3644 protein-species were quantified by iTRAQ during limonene biotransformation (0 and 12 h). A total of 643 proteins were differentially expressed, 316 proteins were significantly up-regulated and 327 proteins were markedly down-regulated. GO, COG, and pathway enrichment analysis showed that the differentially expressed proteins possessed catalytic and binding functions and were involved in a variety of cellular and metabolic process. Furthermore, the enzymes involved in limonene transformation might be related to cytochrome P-450. This study provided a powerful platform for further exploration of biotransformation, and the identified proteins provided insight into the mechanism of limonene transformation.