Search Results (99)

The pathways governing the transformation of crop residues into humic acid (HA) remain incompletely understood because multiple biochemical routes may operate simultaneously during composting-like humification. In this study, a 30-day solid-state humification experiment was conducted by integrating physicochemical pretreatments, including steam explosion (SE) and ammonification coupled with steam explosion (SE-N), with a multi-fungal inoculation strategy involving Aspergillus niger, Candida spp., and Phanerochaete chrysosporium. Across three representative substrate–pretreatment systems and 81 experimental groups, the contents of lignocellulosic fractions, reducing sugars (RS), a UV-280-based soluble nitrogen-containing precursor index (operationally denoted as SNP), fulvic acid (FA), and HA were compared. The results showed that neither physicochemical pretreatment alone nor single-strain inoculation was sufficient to achieve substantial HA formation. SE mainly improved substrate accessibility and promoted carbon release, whereas ammonification provided essential nitrogen preloading for subsequent precursor coupling. In the saccharification-dominant treatment, RS reached 27.5%, but HA remained negligible. In the Candida-only treatment, the soluble nitrogen-containing precursor index increased markedly, yet HA formation was still minimal. By contrast, the highest HA yield (13.7%) was obtained under multi-fungal co-inoculation, particularly when nitrogen preloading by ammonification was combined with concurrent accumulation of carbon and aromatic precursors. The data suggest that lignin-targeting activity by P. chrysosporium was associated with the likely generation of phenolic and quinone-like intermediates that bridged the condensation of sugar- and nitrogen-derived compounds. Overall, the findings support a synergistic humification framework in which polysaccharide depolymerization, microbial nitrogen transformation, and lignin-derived aromatic precursor formation jointly contribute to HA accumulation, rather than a single linear pathway dominating the process. Full article

Steam Explosion (SE) is a relatively newly developed physicochemical pretreatment method that has received increasing attention since it can effectively upgrade biomass for further utilization. During SE, biomass is first exposed to high-temperature, high-pressure steam and then rapidly depressurized. This process efficiently breaks down the lignocellulosic structure, reduces moisture content, and increases fixed carbon and calorific value. It also enhances biomass grindability and densification, making it more suitable as a renewable solid fuel. This review carefully discusses the fundamental principles of SE and its effects on particle characteristics. Then, the types of SE reactors (mainly composed of batch reactors and continuous reactors) are systematically compared, and the challenges in scaling up and commercialization are discussed. Also, the characteristics of pyrolysis or gasification of biomass pretreated by SE are described in detail. Studies indicate that SE is beneficial for the enhancement of product quality. Finally, the prospects and future challenges in the development of SE (including superheated steam explosion, reaction kinetics improvement, and heat and mass transfer intensification) are presented and discussed. Full article

The combination of ammonia and steam explosion pretreatment has shown significant potential to enhance protein yield during the solid-state fermentation (SSF) of rice straw. However, the complex interactions between physicochemical changes and fermentation parameters necessitate precise optimization. This study employed a three-level Box–Behnken design (BBD) within the framework of Response Surface Methodology (RSM) to evaluate the effects of steam explosion pressure, pressure retention time, and ammonia concentration on protein yield. The SSF experiments were conducted in 5 L fermentation bottles using a co-culture of Aspergillus oryzae and Neurospora sitophila. The results demonstrated that the optimal conditions were a pressure of 1.44 MPa, a pressure retention time of 139.4 s, and an ammonia concentration of 8.3%. Under these optimized conditions, the protein yield reached 42.1% after 96 h of SSF, which was validated by a confirmatory experiment (42.8% ± 2.37%). The pretreated rice straw exhibited significantly improved lignocellulose degradation and structural porosity, providing a highly conducive substrate for microbial growth. These findings suggest that the optimized ammonia–steam explosion process is an effective and quantifiable strategy for converting agricultural waste into high-quality protein feed, contributing to sustainable bio-resource utilization. Full article

Mycelium-based composites (MBCs) have emerged as promising biofabricated materials that align with circular economy and clean technology goals by utilizing fungal networks to transform lignocellulosic residues into functional, biodegradable composites. Despite the MBC’s potentials, the intrinsic nature of the fungal strain, substrate physico-chemical composition and engineering property variability remain significant hurdles that should be critically surmounted. Substrate treatment is central to determining growth kinetics, microstructural uniformity, and mechanical performance in MBC production. This review highlights recent advancements in physical, chemical, biological, and hybrid pretreatment methods, including comminution, pasteurization, alkali hydrolysis, enzymatic conditioning, microwave-assisted hydrolysis, ultrasound pretreatment, steam explosion, plasma activation, and irradiation. These technologies collectively enhance substrate digestibility, aeration, and permeability while reducing contamination. Optimization parameters—temperature, pH, C:N ratio, moisture content, particle size, porosity, and aeration—are examined as critical process levers influencing hyphal density, bonding efficiency, and composite uniformity. Evidence suggests that properly engineered substrate treatments accelerate colonization, strengthen hyphal networks, and significantly improve compressive, tensile, and flexural material properties. The review discusses emerging process control tools such as AI-assisted modeling, micro-CT porosity analysis, and sensor-integrated bioreactors that enable reproducible and energy-efficient fabrication. Collectively, the findings position substrate engineering as a foundational technology for scaling high-performance mycelium composites and advancing sustainable material innovation. Full article

To efficiently, sustainably, and rapidly extract bioactive compounds, steam explosion (SE) technology was tried to use for the first time as a pretreatment of Potentilla discolor Bunge (PDB) stems. This study systematically investigated the effects of SE on stem structure, total phenolic content, composition and bioactivities. Macroscopic observation showed that SE-treated stems became darker and deeper in color. Microscopic analysis indicated a reduction in hemicellulose and lignin contents, while the basic skeletal structure remained intact, which facilitated the release of active compounds. This structural modification was directly linked to an enhancement in biological activity. Compared with the untreated group, total phenolic content in SE-treated stems increased 1.11–1.94 times. Correspondingly, antioxidant and hypoglycemic activities were enhanced by 1.35–7.19 times, demonstrating a clear relationship between the structural changes and the improved bioactivity. HPLC analysis showed specific changes in chemical composition, with increased levels of total phenolic content, particularly phenolic acids and flavonoids. Compositional analysis using Q Exactive HF LC-MS and standard comparison revealed that complex macromolecules, such as flavonoid glycosides and polyphenols, were hydrolyzed into smaller, more bioavailable molecules, such as quercetin. Overall, SE pretreatment represents a sustainable and effective approach for improving the extraction of bioactive compounds from PDB stems. These active compounds hold significant potential for applications in functional foods, nutraceuticals, and natural health products, offering an innovative strategy to enhance the bioavailability and bioactivity of plant-derived compounds. Full article

Corn stover (CS) is a promising feedstock for producing fermentable sugars (FS) and ethanol due to its high holocellulose content. This study investigated the enhancement of FS production via enzymatic hydrolysis (EH) following steam explosion (SE) pretreatment of CS, aiming to improve ethanol yields through alcoholic fermentation. SE was conducted at 160 °C, 180 °C, and 200 °C for 2.5 and 10 min. EH was performed using 15 and 30 filter paper unit (FPU) enzyme loadings and 1% and 2% (w/w) substrate concentrations, applied to both untreated CS and pretreated CS (PCS). Fermentations with Saccharomyces cerevisiae were carried out at 30 °C and 120 rpm. The optimal SE condition (200 °C, 10 min) yielded 4.25 g of total sugars per 100 g CS. Under 30 FPU and 2% PCS, EH yielded 41.57 g/100 g PCS and 18.51 g/100 g CS. The combined SE + EH process reached 45.82 g/100 g PCS, about 2.5 times more than EH alone. The highest ethanol concentration and production rate were 15.54 g/L and 1.30 g/L·h, with a yield of 0.47 g/g. Under optimal conditions, fermentation achieved a conversion efficiency of 92.33%. Full article

Lignocellulosic biomass wastes are renewable carbon resources that can be available for conversion into biofuels. There is a growing interest in utilizing a broader range of alternative biomass feedstocks such as agri-crop residues aside from the traditional forest-origin wood residues for fuel pellet production. However, crop residues typically have low and inconsistent fuel quality. This paper investigated the effectiveness of the combined steam explosion and water leaching pretreatment techniques to upgrade the fuel properties of wheat straw. The experimental treatments involved auto-catalyzed steam explosion and acid-catalyzed steam with and without subsequent water leaching. Using steam explosion catalyzed by dilute H₂SO₄ at a low concentration of 0.5 wt%, results showed the highest ash, Si, and Ca removal efficiencies of 82.2%, 91.1%, and 74.3%, respectively. Moreover, there was significant improvement in fuel quality in terms of fuel ratio (0.34) and calorific value HHV (21.9 MJ/kg), as well as a pronounced increase in the comprehensive combustibility index at the devolatization stage, indicating better combustion characteristics. Overall, the results demonstrate that with adequate pretreatment, the quality of agri-pellets derived from wheat straw could potentially be on par with wood pellets that are utilized for heat and power generation and residential heating. To mitigate the dry matter loss due to steam explosion, future studies shall consider using the process effluent to produce biofuel. Full article

This study focused on optimising the saccharification of cardoon mixed residues through acid or base-catalysed steam explosion, using a Response Surface Methodology (RSM) to optimise the main process parameters. Despite the increasing interest in cardoon as a lignocellulosic feedstock, its efficient fractionation remains challenging, with limited cellulose hydrolysis and incomplete hemicellulose recovery under non-optimised steam explosion conditions. Therefore, a systematic evaluation of catalytic severity is required to improve biomass valorisation. H₂SO₄-catalysed steam explosion significantly improved glucan hydrolysis in the following enzymatic saccharification process, achieving 78 mol% glucose yield after a pretreatment carried out at 200 °C, 5 min, and 25 mM catalyst concentration. Xylan recovery required a higher catalyst concentration of 50 mM and temperatures lower than 220 °C to avoid the dehydration reaction of xylose to furfural. The optimal conditions for maximising glucose and xylose yields were 196 °C for 5 min with 50 mM H₂SO₄, resulting in 80.5 mol% glucose yield and 70.3 mol% xylose yield. Alkaline-catalysed steam explosion at 200 °C with 25 mM NaOH increased the enzymatic hydrolysis of glucan and favoured the production of lignin with a higher syringyl/guaiacyl ratio, making it more reactive. Overall, this research provides valuable insights into catalytic steam explosion coupled with the enzymatic saccharification step for the complete valorisation of lignocellulosic cardoon residues. Full article

Valonea, a natural product from Quercus variabilis, is rich in bioactive phenolic compounds; however, its compact physical structure restricts the efficient extraction of these components, limiting its high-value applications. To address this issue, the present study examined the influence of steam explosion (SE) pretreatment on the physical structure, phenolic profile, and bioactivity of valonea and identified optimal processing parameters. Under optimal conditions (1.0 MPa and 10 min), the content of total polyphenols increased by 63.1%, reaching 553.0 mg/g extract, while gallic acid and ellagic acid concentrations increased by 380.6% and 1280.0%, respectively. Electrospray ionization mass spectrometry identified 12 major phenolic constituents, providing a compositional basis for the observed bioactivities. The extract exhibited strong antioxidant and anti-inflammatory properties, confirming that SE not only augments phenolic content but also preserves or enhances the functional quality of the extract. As an efficient and environmentally friendly pretreatment technology, SE substantially improves the bioavailability and activity of phenolics in valonea. Thus, this study offers a reliable strategy for the high-value utilization of valonea in fields such as pharmaceuticals, functional foods, and animal feed. Full article

The effective deconstruction of lignocellulosic biomass is essential for sustainable biorefineries. In this study, corn stover was pretreated by low-alkali (1–5 wt% NaOH) pre-impregnation assisted instant catapult steam explosion (ICSE) to investigate its influence on enzymatic hydrolysis efficiency and the mechanism of lignin-derived anti-enzymatic factors. The results showed that this pretreatment effectively enhanced glucose yield. Under 4–5% NaOH conditions, washed samples achieved glucose yields above 98%. At 4% NaOH, the glucose yields of washed and unwashed groups were 98.88% and 56.34%, respectively, indicating that washing removed soluble inhibitors. LC-MS analysis identified three major water-soluble inhibitory compounds-vanillin, syringaldehyde, and 2-carboxybenzaldehyde-confirming their negative effects on cellulase activity. The alkali-soluble lignin content of unwashed samples (43.28%) was 1.36 times higher than that of washed samples (31.93%), demonstrating its role as a water-insoluble inhibitory factor. Moreover, SEM, XRD, FTIR, and contact angle analyses revealed that 5% NaOH treatment enhanced lignin solubilization, induced structural rearrangement and interfacial hydrophilic reconstruction, and increased cellulose crystallinity and enzyme accessibility. These findings elucidate the mechanistic pathways of lignin transformation and inhibition mitigation, providing valuable insights for efficient and sustainable biomass conversion. Full article

The aim of this study was to check the content of metal inhibitors before and after the pre-treatment of fast-growing poplar wood using steam explosion (SE) at selected temperatures (160, 175, 190 and 205 °C). An X-ray fluorescence spectrometer (XRF) was used for the analysis. The material was analysed after pre-treatment and in its native form in two variants: incinerated wood chips and incinerated wood chips dissolved in nitric acid. The analysis was intended to show the difference in the content of metals inhibiting biological processes, including enzymatic hydrolysis and fermentation (i.e., chromium, manganese, iron, nickel, copper and zinc). The study aimed to identify changes in the content of metallic inhibitors depending on the SE temperature and to demonstrate differences depending on the methodology used to measure metals in the tested material. The greatest change in metal content in the material after pre-treatment was observed for pre-treatment at 175 °C, regardless of the determination method used. Both methods allow the trend in changes in metal content in wood material to be determined. However, due to the heterogeneous structure of wood, the methods give different results, especially for iron. Full article

Nowadays, insects are reared for food and feed. This idea includes the rearing of yellow mealworm (Tenebrio molitor L.). The study aimed to assess the effect of pretreatment of lignocellulosic materials on the growth, survival, and chemical composition of mealworm larvae. The main factor in the experiment was the type of feed. The components of the experimental mixed diets were wheat bran (control feed), enzymatically hydrolysed wheat straw pretreated with steam explosion (WES), enzymatically hydrolysed wheat straw pretreated by the organosolv method (WEO), and enzymatically hydrolysed cup plant pretreated by the organosolv method (CEO) in different combinations with wheat bran. Larval development and survival were monitored and measured. In the final bioassay, larval growth on all feeds containing 10% of pretreated lignocellulosic feed was similar to that of insects reared on the control diet. The specific growth rate of larvae reared on the WEO10 diet was significantly the highest (10.1%). The diet used to feed the insects had a significant effect on the crude protein and crude fat content in their biomass. The highest protein content was found in insects fed wheat bran and fed the CEO10 diet. Protein digestibility averaged 40.7% and did not differ statistically among diets. In conclusion, a moderate inclusion of processed lignocellulosic biomass can be used as a feed component for insect diets. Moreover, insect rearing on such substrates not only enables the utilisation of agricultural residues but also converts them into high-quality protein and fat, which can find applications in the feed, cosmetic, or food industries. Full article

The effective use of biowaste resources becomes crucial for the development of bioprocessing alternatives to current oil- and chemical-based value chains. Targeting the development of multi-product biorefinery approaches benefits the viability and profitability of these process schemes. Certain oleaginous microorganisms, such as oleaginous red yeast, can co-produce industrially relevant bio-based products. This work aims to explore the use of industrial and urban waste as cost-effective feedstock for producing microbial oil and carotenoids using Rhodosporidium toruloides. The soluble fraction, resulting from homogenization, crushing, and centrifugation of discarded vegetable waste, was used as substrate under a pulse-feeding strategy with a concentrated enzymatic hydrolysate from municipal forestry residue obtained after steam explosion pretreatment (190 °C, 10 min, and 40 mg H₂SO₄/g residue). Additionally, the initial nutrient content was investigated to enhance process productivity values. The promising results of these cultivation strategies yield a final cell concentration of 36.4–55.5 g/L dry cell weight (DCW), with an intracellular lipid content of up to 42–45% (w/w) and 665–736 µg/g DCW of carotenoids. These results demonstrate the potential for optimizing the use of waste resources to provide effective alternative uses to current biowaste management practices, also contributing to the market of industrially relevant products with lower environmental impacts. Full article

Cellulosic raw materials are the most common source of carbon on Earth and are in great demand for the production of high-value-added products. Cellulosic feedstocks represent a strong matrix consisting of cellulose, lignin, and hemicelluloses. The efficient transformation of cellulosic raw materials into fermentable sugars requires the use of effective pretreatment strategies. The methods employed for pretreatment should be efficient, have low operating costs, and exhibit lower environmental impact. The present review describes pretreatment methods like liquid hot water (LHW) and steam explosion (SE) and highlights peculiar features, benefits and disadvantages of these processes. The effectiveness of these pretreatment methods and their effect on cellulosic raw materials strongly depends on the type of feedstock (component composition), pretreatment method, and pretreatment conditions (pressure, temperature, time, etc.). The LHW pretreatment requires neither addition of chemicals and catalysts nor grinding stage, but requires high energy inputs. The SE pretreatment is regarded as environmentally friendly and requires lower energy inputs, but contributes to the formation of toxic compounds. The life cycle assessment approach demonstrated that the SE pretreatment outperforms dilute acid pretreatment methods and allows the reduction of energy inputs, thereby improving the environmental performance of the process, while the LHW method improves long-term energy security and creates a greener future. Full article

To examine the humification characteristics of crop residues, three types of crop residues—wheat, maize, and rice—were selected for experimentation. The latter two were subjected to steam explosion (SE) and nitrogen addition SE, respectively. Each of the three types of straw was inoculated in accordance with a specific microbial addition protocol. Furthermore, environmental controls, including the oxygen concentration and temperature type, were employed to enhance the variability of the samples. The results demonstrate statistically significant discrepancies in the concentrations of humic acid (HA) and fulvic acid (FA) between the three samples. Following a 96 h composting process, the highest concentrations of fulvic acid (FA) and humic acid (HA) in the samples were recorded at 10.4% and 15.8%, respectively. This result indicates the successful conversion of crop straw into a high-quality humic acid fertilizer product. Infrared spectroscopy data indicate that the breaking of carbon–carbon bonds and the ring opening, as well as the substitution of benzene rings, occurred during composting, and FA and HA substances were gradually formed. The results indicate that humus production is subject to raw materials, the pre-treatment of materials, the differentiation of strains, and methods of controlling environmental factors. Full article