Integrated approach for extraction of xylose, cellulose, lignin and silica from rice straw

An In Vitro Study on the Role of Cellulases and Xylanases of Bacillus subtilis in Dairy Cattle Nutrition

The administration of Bacilli to dairy cows exerts beneficial effects on dry matter intake, lactation performance, and milk composition, but the rationale behind their efficacy is still poorly understood. In this work, we sought to establish whether cellulases and xylanases, among the enzymes secreted by B. subtilis, are involved in the positive effect exerted by Bacilli on ruminal performance. We took advantage of two isogenic B. subtilis strains, only differing in the secretion levels of those two enzymes. A multi-factorial study was conducted in which eight feed ingredients were treated in vitro, using ruminal fluid from cannulated cows, with cultures of the two strains conveniently grown in a growth medium based on inexpensive waste. Feed degradability and gas production were assessed. Fiber degradability was 10% higher (p < 0.001) in feeds treated with the enzyme-overexpressing strain than in the untreated control, while the non-overexpressing strain provided a 5% increase. The benefit of the fibrolytic enzymes was maximal for maize silage, the most recalcitrant feed. Gas production also correlated with the amount of enzymes applied (p < 0.05). Our results revealed that B. subtilis cellulases and xylanases effectively contribute to improving forage quality, justifying the use of Bacilli as direct-fed microbials to increase animal productivity.

The recovery of aerosol-sized microplastics in highly refractory vegetal matrices for identification by automated Raman microspectroscopy

Ombrotrophic peatlands are fed uniquely by atmospheric inputs and therefore have much potential as temporal archives of atmospheric microplastic (MP) deposition, yet the recovery and detection of MP within an almost purely organic matrix is challenging. This study presents a novel peat digestion protocol using sodium hypochlorite (NaClO) as a reagent for biogenic matrix removal. NaClO is more efficient than hydrogen peroxide (H₂O₂). By using purged air-assisted digestion, NaClO (50 vol%) reached 99% matrix digestion compared with 28% and 75% by H₂O₂ (30 vol%) and Fenton's reagent, respectively. At a concentration of 50 vol% NaClO did however chemically disintegrate small amounts (<10 mass %) of polyethylene terephthalate (PET) and polyamide (PA) fragments in the millimeter size range. Observation of PA6 in natural peat samples, while not found in the procedural blanks, questions whether PA is fully disintegrated by NaClO. The protocol was applied to three commercial sphagnum moss test samples, in which MP particles in the range of 0.8-65.4 μm were detected by Raman microspectroscopy. The MP mass% was determined at 0.012% corresponding to 129 thousand MP particles/g, of which 62% were smaller than 5 μm and 80% were smaller than 10 μm, yet were accountable for only 0.4% (500 ng) and 3.2% (4 μg) of the total mass of MP, respectively. These findings underline the importance of the identification of particles Ø < 5 μm when investigating atmospheric MP deposition. The MP counts were corrected for MP recovery loss and procedural blank contamination. MP spike recovery following the full protocol was estimated at 60%. The protocol offers an efficient way of isolating and pre-concentrating most aerosol sized MPs in large quantities of refractory vegetal matrices and enables the automated μRaman scanning of thousands of particles at a spatial resolution on the order of 1 μm.

A review of the extraction methods and advanced applications of lignin-silica hybrids derived from natural sources

The global trend of increasing energy demand along the large volume of wastewater generated annually from the paper pulping and cellulose production industries are considered as serious dilemma that may need to be solved within these current decades. Within this discipline, lignin, silica or lignin-silica hybrids attained from biomass material have been considered as prospective candidates for the synthesis of advanced materials. In this study, the roles and linking mechanism between lignin and silica in plants were studied and evaluated. The effects of the extraction method on the quality of the obtained material were summarized to show that depending on the biomass feedstocks, different retrieval processes should be considered. The combination of alkaline treatment and acidic pH adjustment is proposed as an effective method to recover lignin-silica with high applicability for various types of raw materials. From considerations of the advanced applications of lignin and silica materials in environmental remediation, electronic devices and rubber fillers future valorizations hold potential in conductive materials and electrochemistry. Along with further studies, this research could not only contribute to the development of zero-waste manufacturing processes but also propose a solution for the fully exploiting of by-products from agricultural production.

Influence of the cellulose purification process on the properties of aerogels obtained from rice straw

Cellulose aerogels were obtained from purified rice straw cellulose fibres (CF) by applying different extraction methods: the conventional alkaline treatment (ALK) and alternative aqueous extraction based on the ultrasound combined with reflux heating (USHT) and subcritical water extraction (SWE) (160 and 180 °C). The composition and properties of the CFs were significantly affected by the purification process. The USHT treatment was as efficient as the ALK at eliminating the silica content, but the fibres maintained a notable ratio of hemicellulose (∼16 %). The SWE treatments were not so effective at removing silica (15 %) but greatly promoted the selective extraction of hemicellulose, especially at 180 °C (3 %). The CF compositional differences affected their hydrogel formation capacity and the properties of aerogels. A higher hemicellulose content in the CF led to better-structured hydrogels with better water-holding capacity, while the aerogels exhibited a more cohesive structure with thicker walls, higher porosity (99 %) and water vapour sorption capacity, but lower liquid water retention capacity (0.2 g/g). The residual silica content also interfered with the hydrogel and aerogel formation, giving rise to less structured hydrogels and more fibrous aerogels, with lower porosity (97-98 %).

Rice husk waste into various template-engineered mesoporous silica materials for different applications: A comprehensive review on recent developments

Following the discovery of Stöber silica, the realm of morphology-controlled mesoporous silica nanomaterials like MCM-41, SBA-15, and KCC-1 has been expanded. Due to their high BET surface area, tunable pores, easiness of functionalization, and excellent thermal and chemical stability, these materials take part a vital role in the advancement of techniques and technologies for tackling the world's largest challenges in the area of water and the environment, energy storage, and biotechnology. Synthesizing these materials with excellent physicochemical properties from cost-efficient biomass wastes is a foremost model of sustainability. Particularly, SiO₂ with a purity >98% can be obtained from rice husk (RH), one of the most abundant biomass wastes, and can be template engineered into various forms of mesoporous silica materials in an economic and eco-friendly way. Hence, this review initially gives insight into why to valorize RH into value-added silica materials. Then the thermal, chemical, hydrothermal, and biological methods of high-quality silica extraction from RH and the principles of synthesis of mesoporous and fibrous mesoporous silica materials like SBA-15, MCM-41, MSNs, and KCC-1 are comprehensively discussed. The potential applications of rice husk-derived mesoporous silica materials in catalysis, drug delivery, energy, adsorption, and environmental remediation are explored. Finally, the conclusion and the future outlook are briefly highlighted.

Comparison of various delignification/desilication pre-treatments and indigenous fungal cellulase for improved hydrolysis of paddy straw

The efficient removal of lignin and silica from paddy straw is essential for its volarization into biofuels and other value-added products. In this work, different chemical pre-treatments viz. acid/alkali, organosolv and deep eutectic solvents were carried out to assess the extent of delignification and desilication of paddy straw. Maximum lignin and silica removal of 96.08 and 95.51% was observed with two step acid (0.5% sulphuric acid) followed by alkali (4% sodium hydroxide) pre-treatment with significantly low total lignin (2.30%) and silica content (0.80%) of the treated straw residue. The treated straw residue contained significantly high holocellulose (91.65%), cellulose (75.01%) and hemicellulose content (16.64%). Among the four indigenous fungal isolates, Penicillium mallochii (JS17) cellulase showed better accessibility for the treated straw residue with maximum release of 504.18 mg g^-1 of reducing sugars and saccharification efficiency of 56.90%. The two-step acid/alkali pre-treatment of paddy straw was highly effective for removing lignin and silica from paddy straw, thereby, resulting in enhanced enzymatic accessibility of the substrate and more efficient hydrolysis of cellulose into fermentable sugars.

Xylose recovery and bioethanol production from sugarcane bagasse pretreated by mild two-stage ultrasonic assisted dilute acid

Pretreatment can improve biomass biodegradability. Here, a novel sugarcane bagasse (SCB) pretreatment process based on two-stage ultrasonic assisted dilute H₂SO₄ (TUDA) under mild conditions was reported. After optimization, the pretreatment was shown to significantly degrade hemicellulose (92.40%) and remove lignin (57.41%) of SCB, leading to reduction of inhibitors and an ethanol fermentation efficiency of 93.37% by SSCF under cellulase 10 FPU/g SCB and 30% pretreated SCB loading. Physical characterization revealed that two-stage ultrasonic could better disrupt SCB than traditional ultrasonic by amplifying the collapse effect and synergistically promoting lignin removal through dilute H₂SO₄. Furthermore, xylose was also effectively recovered from pretreatment supernatant by biochar derived from bagasse. This study established a simple and efficient pretreatment process for high value-added recycling of SCB from solid residue to pretreatment liquid.

Comparative Study on Extraction of Cellulose Fiber from Rice Straw Waste from Chemo-Mechanical and Pulping Method

Inspired by nature, cellulose extracted from plant wastes has been explored, due to its great potential as an alternative for synthetic fiber and filler that contributes to structural performance. The drive of this study was to extract, treat, and evaluate the characteristics of rice straw (RS) (Oryza sativa L.) cellulose as a biodegradable reinforcement to be utilized in polymer base materials. Two routes of extraction and treatment were performed via the pulping (Route 1) and chemo-mechanical methods (Route 2), in order to discover comparative characteristics of the synthesized cellulose fiber. Comprehensive characterization of RS cellulose was carried out to determine crystallinity, surface morphology, and chemical bonding properties, using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infra-red (FTIR), respectively. The XRD test results showed that the crystallinity index (CI) of cellulose powder (CP) decreased after the surface modification treatment, Route 2, from 64.50 to 50.10% CI for modified cellulose powder (MCP), due to the surface alteration of cellulose structure. From Route 1, the crystallinity of the fibers decreased up to 33.5% (dissolve cellulose, DC) after the pulp went through the surface modification and dissolution processes, resulting from the transformation of cellulose phase into para-crystalline structure. FESEM micrographs displayed a significant reduction of raw RS diameter from 7.78 µm to 3.34 µm (treated by Route 1) and 1.06 µm (treated by Route 2). The extracted and treated cellulose via both routes, which was considerably dominated by cellulose II because of the high percentage of alkaline used, include the dissolve cellulose (DC). The dissolution process, using NMMO solvent, was performed on the pulp fiber produced by Route 1. The fiber change from cellulose I to cellulose II after undergoes the process. Thus, the dissolution process maintains cellulose II but turned the pulp to the cellulose solution. The acquired characteristics of cellulose from RS waste, extracted by the employed methods, have a considerably greater potential for further application in numerous industries. It was concluded that the great achievement of extracted RS is obtained the nanosized fibers after surface modification treatment, which is very useful for filler in structural composite applications.

Consecutive Organosolv and Alkaline Pretreatment: An Efficient Approach toward the Production of Cellulose from Rice Straw

The efficient removal of silica from rice straw and separation of its major components is essential for further valorization to produce value-added products. With regard to this, the isolation of cellulose (CEL), hemicellulose (HEM), and lignin (LIG) is imperative but quite challenging. Among several pretreatments of lignocellulosic biomass, the organosolv approach is deemed as one of the promising methods. Here, we present two different two-step approaches for the removal of silica and disintegration of significant components from rice straw, especially CEL; (i) base pretreatment, followed by organosolv treatment in the presence of organic acid, and (ii) organosolv pretreatment in the presence of organic acid, followed by base treatment. After each treatment, the recovered solid components are confirmed by various characterization techniques such as Fourier-transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and thermogravimetric analysis. Method 2 demonstrates 82% total removal of HEM and LIG along with 90.4% of silica removal from rice straw to obtain CEL. Furthermore, the obtained crude CEL is found to be with a purity of 78%. Excellent removal of silica (90.4%) reflects that in a test study, the crude CEL obtained from method 2 gives a higher yield of butyl glucosides (59.6%) than rice straw, which affords 45.0% of butyl glucosides.

Process scale-up of an efficient acid-catalyzed steam pretreatment of rice straw for xylitol production by C. Tropicalis MTCC 6192

The present study focuses on operational parameters for the efficient acid catalyzed rice straw pretreatment process for xylitol production. 75.77 % xylose yield was attained when the 24 h presoaked rice straw (≤10 mm or ≤ 15 mm) in 1.5 % (v/v) H₂SO₄ was pretreated in the same reactor at 121 °C for 30 min. Neutralization with barium hydroxide produced insoluble salt and noticeably reduced HMF and furfurals. Xylitol yield of 0.6 g/g of xylose, was achieved by fermenting rice straw hydrolysate medium with C. tropicalis MTCC 6192. This two-step process of production of xylitol from xylose rich hydrolysate is much simpler and produced minimal inhibitors including organic acids such as acetic acid. This process is modified for upscaling at optimized parameters and will simultaneously minimize the pollution problem caused by rice straw and is also promising for commercial scale.

Application of Ultrasound Pre-Treatment for Enhancing Extraction of Bioactive Compounds from Rice Straw

The extraction of water-soluble bioactive compounds using different green methods is an eco-friendly alternative for valorizing agricultural wastes such as rice straw (RS). In this study, aqueous extracts of RS (particles < 500 µm) were obtained using ultrasound (US), reflux heating (HT), stirring (ST) and a combination of US and ST (USST) or HT (USHT). The extraction kinetics was well fitted to a pseudo-second order model. As regards phenolic compound yield, the US method (342 mg gallic acid (GAE). 100 g-1 RS) was more effective than the ST treatment (256 mg GAE.100 g-1 RS), reaching an asymptotic value after 30 min of process. When combined with HT (USHT), the US pre-treatment led to the highest extraction of phenolic compounds from RS (486 mg GAE.100 g-1 RS) while the extract exhibited the greatest antioxidant activity. Furthermore, the USHT extract reduced the initial counts of Listeria innocua by 1.7 logarithmic cycles. Therefore, the thermal aqueous extraction of RS applying the 30 min US pre-treatment, represents a green and efficient approach to obtain bioactive extracts for food applications.

The effect of a diet based on rice straw co-fermented with probiotics and enzymes versus a fresh corn Stover-based diet on the rumen bacterial community and metabolites of beef cattle

Improvement of the food value of rice straw is urgently required in rice crop growing areas to mitigate pollution caused by rice straw burning and enhance the supply of high-quality forages for ruminants. The aims of the present study were to compare the effects of fresh corn Stover and rice straw co-fermented with probiotics and enzymes on rumen fermentation and establish the feasibility of increasing the rice straw content in ruminant diets and, by extension, reducing air pollution caused by burning rice straw. Twenty Simmental hybrid beef cattle were randomly allotted to two groups with ten cattle per group. They were fed diets based either on rice straw co-fermented with probiotics and enzymes or fresh corn Stover for 90 days. Rumen fluid was sampled with an esophageal tube vacuum pump device from each animal on the mornings of days 30, 60, and 90. Bacterial diversity was evaluated by sequencing the V4–V5 region of the 16S rRNA gene. Metabolomes were analyzed by gas chromatography/time-of-flight mass spectrometry (GC–TOF/MS). Compared to cattle fed fresh corn Stover, those fed rice straw co-fermented with probiotics and enzymes had higher (P < 0.05) levels of acetic acid and propionate in rumen liquid at d 60 and d 90 respectively, higher (P < 0.05) abundances of the phyla Bacteroidetes and Fibrobacteres and the genera Ruminococcus, Saccharofermentans, Pseudobutyrivibrio, Treponema, Lachnoclostridium, and Ruminobacter, and higher (P < 0.05) concentrations of metabolites involved in metabolisms of amino acid, carbohydrate, and cofactors and vitamins. Relative to fresh corn Stover, rice straw co-fermented with probiotics and enzymes resulted in higher VFA concentrations, numbers of complex carbohydrate-decomposing and H₂-utilizing bacteria, and feed energy conversion efficiency in the rumen.