Comparative Study between Direct and Pseudomorphic Transformation of Rice Husk Ash into MFI-Type Zeolite

Alyosef, Hallah Ahmad; Roggendorf, Hans; Schneider, Denise; Inayat, Alexandra; Welscher, Julia; Schwieger, Wilhelm; Münster, Tom; Kloess, Gert; Ibrahim, Suzan S.; Enke, Dirk

doi:10.3390/molecules23010001

Cited by 11 publications

(8 citation statements)

References 24 publications

(42 reference statements)

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“…In the twentieth century cardiac glycosides, the bioactive principles of Digitalis plants replaced the use of extracts. Although other medications have superseded Digitalis in the treatment of heart failure, cardenolides came back into focus as they showed anti-viral and anti-tumoral activity (Prassas and Diamandis 2008 ; Bertol et al 2011 ; Schneider et al 2017 ). Today cardenolides such as digoxin, digitoxin, and lanatoside C are still isolated from Digitalis lanata Ehrh.…”

Section: Introductionmentioning

confidence: 99%

RNAi-mediated gene knockdown of progesterone 5β-reductases in Digitalis lanata reduces 5β-cardenolide content

et al. 2021

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Key message Studying RNAi-mediated DlP5βR1 and DlP5βR2 knockdown shoot culture lines of Digitalis lanata, we here provide direct evidence for the participation of PRISEs (progesterone 5β-reductase/iridoid synthase-like enzymes) in 5β-cardenolide formation. Abstract Progesterone 5β-reductases (P5βR) are assumed to catalyze the reduction of progesterone to 5β-pregnane-3,20-dione, which is a crucial step in the biosynthesis of the 5β-cardenolides. P5βRs are encoded by VEP1-like genes occurring ubiquitously in embryophytes. P5βRs are substrate-promiscuous enone-1,4-reductases recently termed PRISEs (progesterone 5β-reductase/iridoid synthase-like enzymes). Two PRISE genes, termed DlP5βR1 (AY585867.1) and DlP5βR2 (HM210089.1) were isolated from Digitalis lanata. To give experimental evidence for the participation of PRISEs in 5β-cardenolide formation, we here established several RNAi-mediated DlP5βR1 and DlP5βR2 knockdown shoot culture lines of D. lanata. Cardenolide contents were lower in D. lanata P5βR-RNAi lines than in wild-type shoots. We considered that the gene knockdowns may have had pleiotropic effects such as an increase in glutathione (GSH) which is known to inhibit cardenolide formation. GSH levels and expression of glutathione reductase (GR) were measured. Both were higher in the Dl P5βR-RNAi lines than in the wild-type shoots. Cardenolide biosynthesis was restored by buthionine sulfoximine (BSO) treatment in Dl P5βR2-RNAi lines but not in Dl P5βR1-RNAi lines. Since progesterone is a precursor of cardenolides but can also act as a reactive electrophile species (RES), we here discriminated between these by comparing the effects of progesterone and methyl vinyl ketone, a small RES but not a precursor of cardenolides. To the best of our knowledge, we here demonstrated for the first time that P5βR1 is involved in cardenolide formation. We also provide further evidence that PRISEs are also important for plants dealing with stress by detoxifying reactive electrophile species (RES).

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Section: Introductionmentioning

confidence: 99%

RNAi-mediated gene knockdown of progesterone 5β-reductases in Digitalis lanata reduces 5β-cardenolide content

et al. 2021

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“…10-20 wt % of the initial fuel remains as ash rich in silica (i.e., "biogenic silica"). It can be an economically valuable material for various applications including the cement and concrete industry [25][26][27], an adsorbent to remove heavy metal ions such as lead (II), mercury (II), zinc (II) and nickel (II) ions from wastewater streams, as catalyst [28][29][30][31][32][33][34][35][36][37][38], for synthesis of zeolites and mesoporous silica [39][40][41][42][43][44][45][46] or for drug delivery systems [47,48]. Depending on the anticipated application, biogenic silica is required with different purities.…”

Section: Introductionmentioning

confidence: 99%

Generation of High Quality Biogenic Silica by Combustion of Rice Husk and Rice Straw Combined with Pre- and Post-Treatment Strategies—A Review

et al. 2019

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Utilization of biomass either as a renewable energy source or for the generation of biogenic materials has received considerable interest during the past years. In the case of rice husk (RH) and rice straw (RS) with high silica contents in the fuel ash, these approaches can be combined to produce high-grade biogenic silica with purities >98 wt % from combustion residues. The overall process can be considered nearly neutral in terms of CO2 emission and global warming, but it can also address disposal challenges of rice husk and rice straw. For the resulting biogenic silica, several advanced application opportunities exist, e.g., as adsorbents, catalysts, drug delivery systems, etc. This article provides a comprehensive literature review on rice husk and rice straw combustion as well as applied strategies for raw material pre-treatment and/or post-treatment of resulting ashes to obtain high quality biogenic silica. Purity of up to 97.2 wt % SiO2 can be reached by combustion of untreated material. With appropriate fuel pre-treatment and ash post-treatment, biogenic silica with purity up to 99.7 wt % can be achieved. Studies were performed almost exclusively at a laboratory scale.

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“…β-wollastonite was produced from the rice hull ash, as well as calcined limestone via green synthesizing using autoclaving [14]. The rice hull ash, as a silica source, was transformed into MFI-type zeolites (ZSM-5 or Zeolite Socony Mobil-five zeolites) using different structure-directing agents [15].…”

Section: Discussionmentioning

confidence: 99%

Rice Hulls as a Renewable Complex Material Resource

et al. 2018

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As a result of rice grain processing, a big amount of waste (up to 20%) is produced. It is mainly rice hulls. The main components of rice hulls are cellulose, lignin and mineral ash. The mineral ash quantity in rice hulls varies from 15 up to 20%, by weight of the rice hulls. The mineral ash consists of amorphous silica (opal-type). Due to the high content of silica in rice hulls, the material burns with difficulty under natural conditions, and it is biodegradably destroyed only with difficulty, when composted. Utilization of rice hulls then becomes an ecological problem due to huge rice production and its continuous growth. At the same time, the annual quantity of silica content in rice hulls is comparable with the quantity of amorphous silica produced as a mineral resource. The issue of manufacturing cellular glass silica construction materials from rice hulls as a renewable resource is discussed in this paper. The utilization technology is based on an amorphous silicon oxide with the use of energy from the combustion of the organic component of rice hulls.

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Comparative Study between Direct and Pseudomorphic Transformation of Rice Husk Ash into MFI-Type Zeolite

Cited by 11 publications

References 24 publications

RNAi-mediated gene knockdown of progesterone 5β-reductases in Digitalis lanata reduces 5β-cardenolide content

RNAi-mediated gene knockdown of progesterone 5β-reductases in Digitalis lanata reduces 5β-cardenolide content

Generation of High Quality Biogenic Silica by Combustion of Rice Husk and Rice Straw Combined with Pre- and Post-Treatment Strategies—A Review

Rice Hulls as a Renewable Complex Material Resource

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