Production of diosgenin from Dioscorea zingiberensis tubers through enzymatic saccharification and microbial transformation

Isolation of endophytes from Dioscorea nipponica Makino for stimulating diosgenin production and plant growth

KEY MESSAGE

Both bacterial and fungal endophytes exhibited one or more plant growth-promoting (PGP) traits. Among these strains, the Paenibacillus peoriae SYbr421 strain demonstrated the greatest activity in the direct biotransformation of tuber powder from D. nipponica into diosgenin. Endophytes play crucial roles in shaping active metabolites within plants, significantly influencing both the quality and yield of host plants. Dioscorea nipponica Makino accumulates abundant steroidal saponins, which can be hydrolyzed to produce diosgenin. However, our understanding of the associated endophytes and their contributions to plant growth and diosgenin production is limited. The present study aimed to assess the PGP ability and potential of diosgenin biotransformation by endophytes isolates associated with D. nipponica for the efficient improvement of plant growth and development of a clean and effective approach for producing the valuable drug diosgenin. Eighteen bacterial endophytes were classified into six genera through sequencing and phylogenetic analysis of the 16S rDNA gene. Similarly, 12 fungal endophytes were categorized into 5 genera based on sequencing and phylogenetic analysis of the ITS rDNA gene. Pure culture experiments revealed that 30 isolated endophytic strains exhibited one or more PGP traits, such as nitrogen fixation, phosphate solubilization, siderophore synthesis, and IAA production. One strain of endophytic bacteria, P. peoriae SYbr421, effectively directly biotransformed the saponin components in D. nipponica. Moreover, a high yield of diosgenin (3.50%) was obtained at an inoculum size of 4% after 6 days of fermentation. Thus, SYbr421 could be used for a cleaner and more eco-friendly diosgenin production process. In addition, based on the assessment of growth-promoting isolates and seed germination results, the strains SYbr421, SYfr1321, and SYfl221 were selected for greenhouse experiments. The results revealed that the inoculation of these promising isolates significantly increased the plant height and fresh weight of the leaves and roots compared to the control plants. These findings underscore the importance of preparing PGP bioinoculants from selected isolates as an additional option for sustainable diosgenin production.

Identification and a phased pH control strategy of diosgenin bio-synthesized by an endogenous Bacillus licheniformis Syt1 derived from Dioscorea zingiberensis C. H. Wright

Diosgenin is widely used as one precursor of steroidal drugs in pharmaceutical industry. Currently, there is no choice but to traditionally extract diosgenin from Dioscorea zingiberensis C. H. Wright (DZW) or other plants. In this work, an environmentally friendly approach, in which diosgenin can be bio-synthesized by the endophytic bacterium Bacillus licheniformis Syt1 isolated from DZW, is proposed. Diosgenin produced by the strain was identified by high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR). The thermal gravimetric analysis (TGA) showed that the melting point of the diosgenin product was 204 °C. The optical rotation measurement exhibited that the optical rotation was α²⁰₅₈₉ =  - 126.1° ± 1.5° (chloroform, c = 1%): negative sign means that the product is left-handed, which is very important to further produce steroid hormone drugs. Cholesterol may be the intermediate product in the diosgenin biosynthesis pathway. In the batch fermentation process to produce diosgenin using the strain, pH values played an important role. A phased pH control strategy from 5.5 to 7.5 was proved to be more effective to improve production yield than any single pH control, which could get the highest diosgenin yield of 85 ± 8.6 mg L^-1. The proposed method may replace phyto-chemistry extraction to produce diosgenin in the industry in the future.Key points• An endophytic Bacillus licheniformis Syt1 derived from host can produce diosgenin.• A dynamic pH industrial control strategy is better than any single pH control.• Proposed diosgenin-produced method hopefully replaces phyto-chemistry extraction.

Influence of Soil Variation on Diosgenin Content Profile in Costus speciosus from Indo-Gangetic Plains

Costus speciosus is a rich source of commercially important compound Diosgenin, distributed in different regions of India. The present investigation was aimed to quantify diosgenin through High Performance Thin Layer Chromatography in 34 germplasms of Costus speciosus and also to identify the superior sources and to correlate the macronutrients of rhizospheric soil. The starch content varied in microscopic examination and correlated inversely (r=-0.266) with diosgenin content. Findings revealed that the extraction process with acid hydrolysis yielded higher diosgenin content (0.15-1.88 %) as compared to non-hydrolysis (0.009-0.368 %) procedure. Germplasms from Uttar Pradesh (NBCS-4), Jharkhand (NBCS-39) and Bihar (NBCS-2) were identified as elite chemotypes based on hierarchical clustering analysis. The phosphorous content of respective rhizospheric soil correlated positively (r=0.742) with diosgenin content. Findings of present study are useful to identify the new agrotechniques. The elite germplasms can also be used as quality planting material for large scale cultivation in order to assure a sustained supply to the herbal drug industry.

Development of a New Bioprocess for Clean Diosgenin Production through Submerged Fermentation of an Endophytic Fungus

Diosgenin is used widely to synthesize steroidal hormone drugs in the pharmaceutical industry. The conventional diosgenin production process, direct acid hydrolysis of the root of Dioscorea zingiberensis C. H. Wright (DZW), causes large amounts of wastewater and severe environmental pollution. To develop a clean and effective method, the endophytic fungus Fusarium sp. CPCC 400226 was screened for the first time for the microbial biotransformation of DZW in submerged fermentation (SmF). Statistical design and response surface methodology (RSM) were implemented to develop the diosgenin production process using the Fusarium strains. The environmental variables that significantly affected diosgenin yield were determined by the two-level Plackett-Burman design (PBD) with nine factors. PBD indicates that the fermentation period, culture temperature, and antifoam reagent addition are the most influential variables. These three variables were further optimized using the response surface design (RSD). A quadratic model was then built by the central composite design (CCD) to study the impact of interaction and quadratic effect on diosgenin yield. The values of the coefficient of determination for the PBD and CCD models were all over 0.95. P-values for both models were 0.0024 and <0.001, with F-values of ∼414 and ∼2215, respectively. The predicted results showed that a maximum diosgenin yield of 2.22% could be obtained with a fermentation period of 11.89 days, a culture temperature of 30.17 °C, and an antifoam reagent addition of 0.20%. The experimental value was 2.24%, which was in great agreement with predicted value. As a result, over 80% of the steroidal saponins in DZW were converted into diosgenin, presenting a ∼3-fold increase in diosgenin yield. For the first time, we report the SmF of a Fusarium strain used to produce diosgenin through the microbial biotransformation of DZW. A practical diosgenin production process was established for the first time for Fusarium strains. This bioprocess is acid-free and wastewater-free, providing a promising environmentally friendly alternative to diosgenin production in industrial applications. The information provided in the current study may be applicable to produce diosgenin in SmF by other endophytic fungi and lays a solid foundation for endophytic fungi to produce natural products.

The Application of Fermentation Technology in Traditional Chinese Medicine: A Review

In Chinese medicine, fermentation is a highly important processing technology whereby medicinal herbs are fermented under appropriate temperature, humidity, and moisture conditions by means of the action of microorganisms to enhance their original characteristics and/or produce new effects. This expands the scope of such medicines and helps them to meet the stringent demands of clinical application. Since ancient times, Chinese medicine has been made into Yaoqu to reduce its toxicity and increase its efficiency. Modern fermentation technologies have been developed on the basis of traditional fermentation techniques and modern biological technology, and they can be divided into solid fermentation, liquid fermentation, and two-way fermentation technologies according to the fermentation form employed. This review serves as an introduction to traditional fermentation technology and its related products, modern fermentation technologies, and the application of fermentation technology in the field of Chinese medicine. Several problems and challenges facing the field are also briefly discussed.

Biotic elicitors enhance diosgenin production in Helicteres isora L. suspension cultures via up-regulation of CAS and HMGR genes

In an attempt to find an alternative and potent source of diosgenin, a steroidal saponin in great demand for its pharmaceutical importance, Helicteres isora suspension cultures were explored for diosgenin extraction. The effect of biotic elicitors on the biosynthesis of diosgenin, in suspension cultures of H. isora was studied. Bacterial as well as fungal elicitors such as Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and Aspergillus niger were applied at varying concentrations to investigate their effects on diosgenin content. The HPLC based quantification of the treated samples proved that amongst the biotic elicitors, E. coli (1.5%) proved best with a 9.1-fold increase in diosgenin content over respective control cultures. Further, the scaling-up of the suspension culture to shake-flask and ultimately to bioreactor level were carried out for production of diosgenin. During all the scaling-up stages, diosgenin yield obtained was in the range between 7.91 and 8.64 mg l^-1, where diosgenin content was increased with volume of the medium. The quantitative real-time PCR (qRT-PCR) analysis showed biotic elicitors induced the expression levels of regulatory genes in diosgenin biosynthetic pathway, the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and cycloartenol synthase (CAS), which can be positively correlated with elicited diosgenin contents in those cultures. The study holds significance as H. isora represents a cleaner and easy source of diosgenin where unlike other traditional sources, it is not admixed with other steroidal saponins, and the scaled-up levels of diosgenin achieved herein have the potential to be explored commercially.

Recent Advances in Biotransformation of Saponins

Saponins are a class of glycosides whose aglycones can be either triterpenes or helical spirostanes. It is commonly recognized that these active ingredients are widely found in various kinds of advanced plants. Rare saponins, a special type of the saponins class, are able to enhance bidirectional immune regulation and memory, and have anti-lipid oxidation, anticancer, and antifatigue capabilities, but they are infrequent in nature. Moreover, the in vivo absorption rate of saponins is exceedingly low, which restricts their functions. Under such circumstances, the biotransformation of these ingredients from normal saponins—which are not be easily adsorbed by human bodies—is preferred nowadays. This process has multiple advantages, including strong specificity, mild conditions, and fewer byproducts. In this paper, the biotransformation of natural saponins—such as ginsenoside, gypenoside, glycyrrhizin, saikosaponin, dioscin, timosaponin, astragaloside and ardipusilloside—through microorganisms (Aspergillus sp., lactic acid bacteria, bacilli, and intestinal microbes) will be reviewed and prospected.

Effects of an Endophytic Fungus Umbelopsis dimorpha on the Secondary Metabolites of Host-Plant Kadsura angustifolia

Fungal endophytes live widely inside plant tissues and some have been revealed to provide benefits to their host and ecological environment. Considering the fact that endophytes are engaged in remarkably stable long-term interactions with the host for their whole life cycle, it's conceivable that both partners have substantial influence on each other's metabolic processes. Here, we investigated the fermented products of an endophytic fungus Umbelopsis dimorpha SWUKD3.1410 grown on host-plant Kadsura angustifolia and wheat bran, respectively, to assess the impact of SWUKD3.1410 on the secondary metabolites of K. angustifolia. Twenty compounds (1-20) were isolated and identified as 11 schitriterpenoids (1-9, 17-18), two lignans (10, 20), two sesquiterpenoids (11-12), one trinorsesquiterpenoid (13), one monoterpene (14), one sterol (19), and two simple aromatic compounds (15-16) by the extensive 1D-, 2D-NMR and HR-ESI-MS data analysis. Except for nigranoic acid (1), compounds 2-19 have been firstly found from K. angustifolia. Of them, metabolites 2, 11, and 14 were identified to be new. Obtained results indicated that U. dimorpha SWUKD3.1410 could not only produce the same/similar components as its host does, and modify the host-plant components, but also enhance the production of these highly oxygenated schitriterpenoids/schinortriterpenoids in plants. This study suggested an interesting prospective for setting up alternative processing techniques to improve the quality of crude drugs derived from K. angustifolia and increase their values.

Recent advances in steroidal saponins biosynthesis and in vitro production

Steroidal saponins exhibited numerous pharmacological activities due to the modification of their backbone by different cytochrome P450s (P450) and UDP glycosyltransferases (UGTs). Plant-derived steroidal saponins are not sufficient for utilizing them for commercial purpose so in vitro production of saponin by tissue culture, root culture, embryo culture, etc, is necessary for its large-scale production. Saponin glycosides are the important class of plant secondary metabolites, which consists of either steroidal or terpenoidal backbone. Due to the existence of a wide range of medicinal properties, saponin glycosides are pharmacologically very important. This review is focused on important medicinal properties of steroidal saponin, its occurrence, and biosynthesis. In addition to this, some recently identified plants containing steroidal saponins in different parts were summarized. The high throughput transcriptome sequencing approach elaborates our understanding related to the secondary metabolic pathway and its regulation even in the absence of adequate genomic information of non-model plants. The aim of this review is to encapsulate the information related to applications of steroidal saponin and its biosynthetic enzymes specially P450s and UGTs that are involved at later stage modifications of saponin backbone. Lastly, we discussed the in vitro production of steroidal saponin as the plant-based production of saponin is time-consuming and yield a limited amount of saponins. A large amount of plant material has been used to increase the production of steroidal saponin by employing in vitro culture technique, which has received a lot of attention in past two decades and provides a way to conserve medicinal plants as well as to escape them for being endangered.

Isolation of endophytic fungi from Dioscorea zingiberensis C. H. Wright and application for diosgenin production by solid-state fermentation

In this study, endophytic fungi were isolated from Dioscorea zingiberensis C.H. Wright (DZW), and a novel clean process to prepare diosgenin from DZW was developed. A total of 123 strains of endophytic fungi were isolated from different plant tissues of DZW. Among them, the strain Fusarium sp. (CPCC 400709) showed the best activity of hydrolyzing steroidal saponins in DZW into diosgenin. Thus, this strain was used to prepare diosgenin from DZW by solid-state fermentation. The fermentation parameters were optimized using response surface methodology, and a high yield of diosgenin (2.16%) was obtained at 14.5% ammonium sulfate, an inoculum size of 12.3%, and 22 days of fermentation. Furthermore, the highest diosgenin yield (2.79%) was obtained by co-fermentation with Fusarium sp. (CPCC 400709) and Curvularia lunata (CPCC 400737), which was 98.9% of that obtained by β-glucosidase pretreated acid hydrolysis (2.82%). This process is acid-free and wastewater-free, and shows promise as an effective and clean way to prepare diosgenin for use in industrial applications from DZW.

Acute toxicity and genotoxicity study of fermented traditional herb formula Guibi-tang

ETHNOPHARMACOLOGY RELEVANCE

Guibi-tang (Guipi-tang in Chinese and Kihi-to in Japanese) is a multi-herb traditional medicine commonly prescribed to treat psychoneurosis in East Asia. Although this medicine has been widely used, there is little available information on the safety and toxicity of Guibi-tang, especially on the fermented one.

MATERIALS AND METHODS

Guibi-tang, composed of 12 herbs, was fermented with bacteria and lyophilized. Single dose acute toxicity in rats was observed for 14 days after administration. Genetic toxicity of fermented Guibi-tang was evaluated on bacterial reverse mutation in Salmonella and Escherichia spp., chromosome aberrations in Chinese hamster ovary cells, and micronucleus formation in mice. Ingredients in FGBT were identified and quantified by high performance liquid chromatography-mass spectrometry.

RESULTS

In acute oral toxicity study, behavior, clinical signs and body weight changes were normal observing in all experimental animals. No revertant colonies were found in any bacterial cultures examined. Morphological or numerical anomalies and significant increased number of aberrant metaphases were not observed. Micronucleus assay showed no significant increases in the frequency of inducing micronuclei in any dose examined. Decursinol, decursin, glycyrrhizin, and 6-gingerol in fermented Guibi-tang were identified and quantitated. As a whole, no acute and genotoxic effects were found in all the assays and parameters analyzed.

CONCLUSION

Fermented Guibi-tang was recognized as safe and non-toxic, and therefore can be used for applications of traditional medicine in modern complementary and alternative therapeutics and health care.

Evaluation of different pretreatments on microbial transformation of saponins in Dioscorea zingiberensis for diosgenin production

In order to evaluate the effects of different pretreatments on microbial transformation of saponins in Dioscorea zingiberensis (DZW), various methods have been systematically studied on a large scale. Five pretreatments, including physical separation, catalytic solvent extraction, ultrasonic fermentation, complex enzymatic hydrolyzation and enzymatic saccharification, were performed on DZW. Compared with other methods, complex enzymatic hydrolyzation significantly improved the efficiency of microbial transformation. Due to the pretreatment, a diosgenin yield of 92.6%, and diosgenin accumulation of 27.3 mg/g DZW were achieved. The high efficiency of this method was attributed to the separation of 84.3% starch and 76.5% fibre from DZW in the form of a sugar. Analysis of saponins in this microbial transformation process showed that the residual rates of the intermediate products were much lower than those obtained from other pretreatments. The results demonstrate that complex enzymatic hydrolyzation is a practical and effective pretreatment method for production of diosgenin from DZW in a microbial transformation way.

Screening for differentially expressed genes in endophytic fungus strain 39 during co-culture with herbal extract of its host Dioscorea nipponica Makino

Strain 39 is an endophytic fungus which was isolated from Dioscorea nipponica Makino (DNM). After Strain 39 co-cultured with ethanol extract of DNM rhizomes for several days, the content of saponins in this culture mixture would be obviously increased. To analyze the mechanism of this microbial transformation, we used the differential display reverse transcription polymerase chain reaction (DDRT-PCR) method to compare the transcriptomes between Strain 39 cultured in normal PD medium and in PD medium which added ethanol extract of DNM rhizomes. We amplified 29 DDRT-PCR bands using 12 primer combinations of three anchored primers and five random primers, and six bands were re-amplified. Analysis of real-time PCR and sequence alignment showed that three clones were up-regulated in sample group: squalene epoxidase, squalene synthase, and catalase, one clone was expressed only in sample group. The possible roles and origins of the above genes were discussed, and the molecular mechanism of Strain 39 biotransformation was speculated. This study is the first report of the molecular biotransformation mechanism of saponins production by endophytic fungus of DNM.

Recent biotechnological progress in enzymatic synthesis of glycosides

Glycosylation is one of the most important post-modification processes of small molecules and enables the parent molecule to have increased solubility, stability, and bioactivity. Enzyme-based glycosylation has achieved significant progress due to advances in protein engineering, DNA recombinant techniques, exploitation of biosynthetic gene clusters of natural products, and computer-based modeling programs. Our report summarizes glycosylation data that have been published within the past five years to provide an overall review of current progress. We also present the future trends and perspectives for glycosylation.

Preparation of progenin III from total steroidal saponins of Dioscorea nipponica Makino using a crude enzyme from Aspergillus oryzae strain

Progenin III, one of the most active spirostanol saponins, is a potential candidate for anti-cancer therapy due to its strong antitumor activity and low hemolytic activity. However, the concentration of progenin III is extremely low in natural Dioscorea plants. In this paper, the progenin III production from total steroidal saponins of Dioscorea nipponica Makino was studied using the crude enzyme from Aspergillus oryzae DLFCC-38. The crude enzyme converting total steroidal saponins into progenin III was obtained from the A. oryzae DLFCC-38 culture. For enzyme production, the strain was cultured for 72 h at 30 °C with shaking at 150 rpm in 5 % (w/v) malt extract medium containing 2 % (v/v) extract of D. nipponica as the enzyme inducer. The crude enzyme converted total steroidal saponins into major progenin III with a high yield when the reaction was carried out for 9 h at 50 °C and pH 5.0 with the 20 mg/ml of substrate. In the preparation of progenin III, 117 g of crude progenin III was obtained from 160 g of substrate, and the crude product was purified with silica gel column to obtain 60.3 g progenin III of 93.4 % purity.