Determination of cell wall ferulic and p-coumaric acids in sugarcane bagasse

Beyond low lignin: Identifying the primary barrier to plant biomass conversion by fermentative bacteria

Renewable alternatives for nonelectrifiable fossil-derived chemicals are needed and plant matter, the most abundant biomass on Earth, provide an ideal feedstock. However, the heterogeneous polymeric composition of lignocellulose makes conversion difficult. Lignin presents a formidable barrier to fermentation of nonpretreated biomass. Extensive chemical and enzymatic treatments can liberate fermentable carbohydrates from plant biomass, but microbial routes offer many advantages, including concomitant conversion to industrial chemicals. Here, testing of lignin content of nonpretreated biomass using the cellulolytic thermophilic bacterium, Anaerocellum bescii, revealed that the primary microbial degradation barrier relates to methoxy substitutions in lignin. This contrasts with optimal lignin composition for chemical pretreatment that favors high S/G ratio and low H lignin. Genetically modified poplar trees with diverse lignin compositions confirm these findings. In addition, poplar trees with low methoxy content achieve industrially relevant levels of microbial solubilization without any pretreatments and with no impact on tree fitness in greenhouse.

Aqueous Pretreatment of Lignocellulosic Biomass for Binderless Material Production: Influence of Twin-Screw Extrusion Configuration and Liquid-to-Solid Ratio

This study was carried out to investigate the continuous aqueous pretreatment of sugarcane bagasse (SCB) through twin-screw extrusion for a new integrated full valorization, where the solid residue (extrudate) was used for the production of bio-based materials by thermocompression and the filtrate for the production of high-value-added molecules. Two configurations, with and without a filtration module, were tested and the influence of the SCB composition and structure on the properties of the materials were determined. The impact of the liquid-to-solid (L/S) ratio was studied (0.65-6.00) in relation to the material properties and the biomolecule extraction yield in the filtrate (with the filtration configuration). An L/S ratio of at least 1.25 was required to obtain a liquid filtrate, and increasing the L/S ratio to 2 increased the extraction yield to 11.5 g/kg of the inlet SCB. The extrudate obtained without filtration yielded materials with properties equivalent to those obtained with filtration for L/S ratios of at least 1.25. Since the molecule extraction process was limited, a configuration without filtration would make it possible to reduce water consumption in the process while obtaining high material properties. Under the filtration configuration, an L/S ratio of 2 was the best tradeoff between water consumption, extraction yield, and the material properties, which included 1485 kg/m3 density, 6.2 GPa flexural modulus, 51.2 MPa flexural strength, and a water absorption (WA) and thickness swelling (TS) of 37% and 44%, respectively, after 24 h of water immersion. The aqueous pretreatment by twin-screw extrusion allowed for the overall valorization of SCB, resulting in materials with significantly improved properties compared to those obtained with raw SCB due to fiber deconstruction.

Improved antioxidant activity of pretreated lignin nanoparticles: Evaluation and self-assembly

Lignin nanoparticles (LNPs) have gained significant attention for their potential as natural antioxidants. This study investigated the effect of various pretreatment methods on the lignin structure and subsequent antioxidant activity of LNPs. Among four pretreated LNPs, hydrothermal LNPs exhibited the highest antioxidant activity, surpassing unpretreated, acid-pretreated and kraft LNPs, with an impressive efficacy of 91.6%. The relationship between LNPs' structure and antioxidant activity was revealed by 2D heteronuclear singular quantum correlation (1H13C HSQC) and 31P nuclear magnetic resonance (NMR). 1H13C HSQC suggested the cleavage of β-O-4 ether bonds, as well as a decrease in ferulic acid and p-coumaric acid, which directly influenced the antioxidant activity of LNPs. 31P NMR demonstrated a positive correlation between the total hydroxyl group content and the antioxidant activity. Besides, an isothermal kinetic model for scavenging free radicals was established based on Langmuir kinetic model instead of Freundlich model. Moreover, multilayer LNPs, based on layer-by-layer self-assembly, were prepared and exhibited remarkable antioxidant activity of 95.8%. More importantly, when blended with pure cosmetic cream, the multilayer LNPs maintained antioxidant activity of 86.7%. These finding may promote the practical applications of biomolecules, e.g. lignin additives in cosmetics and pharmaceuticals.

Effect of different sterilization methods on the appearance, composition, and flavor of sugarcane juice

Cold-pressed sugarcane juice (SCJ) is a beverage rich in vitamins, carbohydrates, and antioxidants. Various sterilization methods impact fruit juice's appearance, nutrients, and flavor. Hence, this study aims to assess how different sterilization techniques affect the flavor, appearance, and nutritional value of SCJ. Freshly prepared SCJs were subjected to two sterilization methods: pasteurization (referred to as PTG) and autoclaving (referred to as HTHP). The pasteurization process was carried out at 63°C for 30 min, whereas the HTHP process was applied at 115°C for 30 min. The appearances, Brix value, colors, sugar, organic acid content, and aromatic compounds were determined. The Brix and pH values of the juice show little variation across different heat treatments. The color index of PTG was similar to that of the control group, whereas the L* value of HTHP increased about 21%, resulting in a significant color change. The glucose and fructose contents of HTHP were 7.03 and 5.41 mg/mL, which were much higher than those of PTG (3.26 and 2.33 mg/mL) and control group (3.33 and 2.48 mg/mL). A total of 77 aromatic compounds were identified in the SCJ after various heat treatments. Among them, pentanoic acid, octanal, and β-damascenone were the most abundant substances contributing to the overall flavor in the control group, PTG, and HTHP. Pasteurization preserved the original flavor of the juice, whereas autoclaving triggered the Maillard reaction, forming pyrazine and furan-like compounds that altered the SCJ's flavor. In conclusion, pasteurization retained SCJ's original characteristics, whereas HTHP induces changes in nutrition and imparts a distinct flavor.

Variable lignin structure revealed in Populus leaves

Lignin has long been a trait of interest, especially in bioenergy feedstocks such as Populus. While the stem lignin of Populus is well studied, foliar lignin has received significantly less consideration. To this end, leaves from 11 field grown, natural variant Populus trichocarpa genotypes were investigated by NMR, FTIR, and GC-MS. Five of these genotypes were sufficiently irrigated, and the other six genotypes were irrigated at a reduced rate (59% of the potential evapotranspiration for the site) to induce drought treatment. Analysis by HSQC NMR revealed highly variable lignin structure among the samples, especially for the syringyl/guaiacyl (S/G) ratio, which ranged from 0.52-11.9. Appreciable levels of a condensed syringyl lignin structure were observed in most samples. The same genotype subjected to different treatments exhibited similar levels of condensed syringyl lignin, suggesting this was not a response to stress. A cross peak of δ_C/δ_H 74.6/5.03, consistent with the erythro form of the β-O-4 linkage, was observed in genotypes where significant syringyl units were present. Principle component analysis revealed that FTIR absorbances associated with syringyl units (830 cm^-1, 1317 cm^-1) greatly contributed to variability between samples. Additionally, the ratio of 830/1230 cm^-1 peak intensities were reasonably correlated (p-value < 0.05) with the S/G ratio determined by NMR. Analysis by GC-MS revealed significant variability of secondary metabolites such as tremuloidin, trichocarpin, and salicortin. Additionally, salicin derivatives were found to be well correlated with NMR results, which has been previously hypothesized. These results highlight previously unexplored nuance and variability associated with foliage tissue of poplar.

Cell wall response of field grown Populus to Septoria infection

Due to its ability to spread quickly and result in tree mortality, Sphaerulina musiva (Septoria) is one of the most severe diseases impacting Populus. Previous studies have identified that Septoria infection induces differential expression of phenylpropanoid biosynthesis genes. However, more extensive characterization of changes to lignin in response to Septoria infection is lacking. To study the changes of lignin due to Septoria infection, four field grown, naturally variant Populus trichocarpa exhibiting visible signs of Septoria infection were sampled at health, infected, and reaction zone regions for cell wall characterization. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and acid hydrolysis were applied to identify changes to the cell wall, and especially lignin. FTIR and subsequent principal component analysis revealed that infected and reaction zone regions were similar and could be distinguished from the non-infected (healthy) region. NMR results indicated the general trend that infected region had a higher syringyl:guaiacyl ratio and lower p-hydroxybenzoate content than the healthy regions from the same genotype. Finally, Klason lignin content in the infected and/or reaction zone regions was shown to be higher than healthy region, which is consistent with previous observations of periderm development and metabolite profiling. These results provide insights on the response of Populus wood characteristics to Septoria infection, especially between healthy and infected region within the same genotype.

Sustainable biosynthetic pathways to value-added bioproducts from hydroxycinnamic acids

The biorefinery concept, in which biomass is utilized for the production of fuels and chemicals, emerges as an eco-friendly, cost-effective, and renewable alternative to petrochemical-based production. The hydroxycinnamic acid fraction of lignocellulosic biomass represents an untapped source of aromatic molecules that can be converted to numerous high-value products with industrial applications, including in the flavor and fragrance sector and pharmaceuticals. This review describes several biochemical pathways useful in the development of a biorefinery concept based on the biocatalytic conversion of the hydroxycinnamic acids ferulic, caffeic, and p-coumaric acid into high-value molecules. KEY POINTS: • The phenylpropanoids bioconversion pathways in the context of biorefineries • Description of pathways from hydroxycinnamic acids to high-value compounds • Metabolic engineering and synthetic biology advance hydroxycinnamic acid-based biorefineries.

ART1 and putrescine contribute to rice aluminum resistance via OsMYB30 in cell wall modification

Cell wall is the first physical barrier to aluminum (Al) toxicity. Modification of cell wall properties to change its binding capacity to Al is one of the major strategies for plant Al resistance; nevertheless, how it is regulated in rice remains largely unknown. In this study, we show that exogenous application of putrescines (Put) could significantly restore the Al resistance of art1, a rice mutant lacking the central regulator Al RESISTANCE TRANSCRIPTION FACTOR 1 (ART1), and reduce its Al accumulation particularly in the cell wall of root tips. Based on RNA-sequencing, yeast-one-hybrid and electrophoresis mobility shift assays, we identified an R2R3 MYB transcription factor OsMYB30 as the novel target in both ART1-dependent and Put-promoted Al resistance. Furthermore, transient dual-luciferase assay showed that ART1 directly inhibited the expression of OsMYB30, and in turn repressed Os4CL5-dependent 4-coumaric acid accumulation, hence reducing the Al-binding capacity of cell wall and enhancing Al resistance. Additionally, Put repressed OsMYB30 expression by eliminating Al-induced H₂ O₂ accumulation, while exogenous H₂ O₂ promoted OsMYB30 expression. We concluded that ART1 confers Put-promoted Al resistance via repression of OsMYB30-regulated modification of cell wall properties in rice.

Role of cell-substrate association during plant biomass solubilization by the extreme thermophile Caldicellulosiruptor bescii

Caldicellulosiruptor species are proficient at solubilizing carbohydrates in lignocellulosic biomass through surface (S)-layer bound and secretomic glycoside hydrolases. Tāpirins, surface-associated, non-catalytic binding proteins in Caldicellulosiruptor species, bind tightly to microcrystalline cellulose, and likely play a key role in natural environments for scavenging scarce carbohydrates in hot springs. However, the question arises: If tāpirin concentration on Caldicellulosiruptor cell walls increased above native levels, would this offer any benefit to lignocellulose carbohydrate hydrolysis and, hence, biomass solubilization? This question was addressed by engineering the genes for tight-binding, non-native tāpirins into C. bescii. The engineered C. bescii strains bound more tightly to microcrystalline cellulose (Avicel) and biomass compared to the parent. However, tāpirin overexpression did not significantly improve solubilization or conversion for wheat straw or sugarcane bagasse. When incubated with poplar, the tāpirin-engineered strains increased solubilization by 10% compared to the parent, and corresponding acetate production, a measure of carbohydrate fermentation intensity, was 28% higher for the Calkr_0826 expression strain and 18.5% higher for the Calhy_0908 expression strain. These results show that enhanced binding to the substrate, beyond the native capability, did not improve C. bescii solubilization of plant biomass, but in some cases may improve conversion of released lignocellulose carbohydrates to fermentation products.

High-efficiency novel extraction process of target polyphenols using enzymes in hydroalcoholic media

Agro-industrial by-products are a sustainable source of natural additives that can replace the synthetic ones in the food industry. Grape pomace is an abundant by-product that contains about 70% of the grape's polyphenols. Polyphenols are natural antioxidants with multiple health-promoting properties. They are secondary plant metabolites with a wide range of solubilities. Here, a novel extraction process of these compounds was developed using enzymes that specifically liberates target polyphenols in the appropriate hydroalcoholic mixture. Tannase, cellulase, and pectinase retained 22, 60, and 52% of their activity, respectively, in ethanol 30% v/v. Therefore, extractions were tested in ethanol concentrations between 0 and 30% v/v. Some of these enzymes presented synergistic effects in the extraction of specific polyphenols. Maximum yield of gallic acid was obtained using tannase and pectinase enzymes in ethanol 10% v/v (49.56 ± 0.01 mg L^-1 h^-1); in the case of p-coumaric acid, by cellulase and pectinase treatment in ethanol 30% v/v (7.72 ± 0.26 mg L^-1 h^-1), and in the case of trans-resveratrol, by pectinase treatment in ethanol 30% v/v (0.98 ± 0.04 mg L^-1 h^-1). Also, the effect of enzymes and solvent polarity was analysed for the extraction of malvidin-3-O-glucoside, syringic acid, and quercetin. Previous studies were mainly focused on the maximization of total polyphenols extraction yields, being the polyphenolic profile the consequence but not the driving force of the optimization. In the present study, the basis of a platform for a precise extraction of the desire polyphenols is provided. KEY POINTS: • Enzymes can be used up to ethanol 30% v/v. • The specific enzymes' action determines the polyphenolic profile of the extracts. • The yields obtained of target polyphenols are competitive.

Cocoa bean shells: a review into the chemical profile, the bioactivity and the biotransformation to enhance their potential applications in foods

During processing, cocoa bean shells (CBS) are de-hulled from the bean and discarded as waste. Undermined by its chemical and bioactive composition, CBS is abundant in dietary fiber and phenolic compounds that may serve the valorization purpose of this by-product material into prebiotic and functional ingredients. In addition, the cell-wall components of CBS can be combined through enzymatic feruloylation to obtain feruloylated oligo- and polysaccharides (FOs), further enhancing the techno-functional properties. FOs have attracted scientific attention due to their prebiotic, antimicrobial, anti-inflammatory and antioxidant functions inherent to their structural features. This review covers the chemical and bioactive compositions of CBS as well as their modifications upon cocoa processing. Physical, chemical, and enzymatic approaches to extract and bio-transform bioactive components from the cell wall matrix of CBS were also discussed. Although nonspecific to CBS, studies were compiled to investigate efforts done to extract and produce feruloylated oligo- and polysaccharides from the cell wall materials.

Construction of ferulic acid modified porous starch esters for improving the antioxidant capacity

For exploration of a type of synthetic antioxidant dietary fiber (ADF), porous starch (PS), modified by esterification with ferulic acid (FA) moieties, was synthesized successfully, with different degree of substitution (DS). The ester linkage of FA modified PS was confirmed by 13C solid-state NMR and FT-IR. XRD analysis showed that starch ferulates had a different crystal structure from the V-type pattern of native starch, suggesting that the starch gelled during the esterification reaction, then re-crystallized into a different structure. Morphological studies revealed that FA modified PS esters had a different morphology of irregular beehive-like and dense fibrous-like structures compared with that of native starch. In vitro antioxidant assays showed that starch ferulates had excellent antioxidant capacity. In particular, FA modified PS esters had a much higher antioxidant capacity than free FA in the β-carotene-linoleic acid assay. This study has advanced the technology of using porous starches for modifying the biological activity of an antioxidant polyphenol. We expect this work would inspire further studies on the interactions of phenolics with other food ingredients in the food industry.

Guiding stars to the field of dreams: Metabolically engineered pathways and microbial platforms for a sustainable lignin-based industry

Lignin is an important structural component of terrestrial plants and is readily generated during biomass fractionation in lignocellulose processing facilities. Due to lacking alternatives the majority of technical lignins is industrially simply burned into heat and energy. However, regarding its vast abundance and a chemically interesting richness in aromatics, lignin is presently regarded as the most under-utilized and promising feedstock for value-added applications. Notably, microbes have evolved powerful enzymes and pathways that break down lignin and metabolize its various aromatic components. This natural pathway atlas meanwhile serves as a guiding star for metabolic engineers to breed designed cell factories and efficiently upgrade this global waste stream. The metabolism of aromatic compounds, in combination with success stories from systems metabolic engineering, as reviewed here, promises a sustainable product portfolio from lignin, comprising bulk and specialty chemicals, biomaterials, and fuels.

Scavenging Properties of Plant-Derived Natural Biomolecule Para-Coumaric Acid in the Prevention of Oxidative Stress-Induced Diseases

Para-coumaric acid (p-CA) is a plant derived secondary metabolite belonging to the phenolic compounds. It is widely distributed in the plant kingdom and found mainly in fruits, vegetables, and cereals. Various in vivo and in vitro studies have revealed its scavenging and antioxidative properties in the reduction of oxidative stress and inflammatory reactions. This evidence-based review focuses on the protective role of p-CA including its therapeutic potential. p-CA and its conjugates possesses various bioactivities such as antioxidant, anti-inflammatory, anti-cancer, anti-diabetic, and anti-melanogenic properties. Due to its potent free radical scavenging activity, it can mitigate the ill effects of various diseases including arthritis, neurological disorders, and cardio-vascular diseases. Recent studies have revealed that p-CA can ameliorate the harmful effects associated with oxidative stress in the reproductive system, also by inhibiting enzymes linked with erectile function.

The Potential of Grape Pomace Varieties as a Dietary Source of Pectic Substances

Grape pomace is one of the most abundant solid by-products generated during winemaking. A lot of products, such as ethanol, tartrates, citric acid, grape seed oil, hydrocolloids, bioactive compounds and dietary fiber are recovered from grape pomace. Grape pomace represents a major interest in the field of fiber extraction, especially pectin, as an alternative source to conventional ones, such as apple pomace and citrus peels, from which pectin is obtained by acid extraction and precipitation using alcohols. Understanding the structural and functional components of grape pomace will significantly aid in developing efficient extraction of pectin from unconventional sources. In recent years, natural biodegradable polymers, like pectin has invoked a big interest due to versatile properties and diverse applications in food industry and other fields. Thus, pectin extraction from grape pomace could afford a new reason for the decrease of environmental pollution and waste generation. This paper briefly describes the structure and composition of grape pomace of different varieties for the utilization of grape pomace as a source of pectin in food industry.

Variable and dose-dependent response of Saccharomyces and non-Saccharomyces yeasts toward lignocellulosic hydrolysate inhibitors

Lignocellulosic hydrolysates will also contain compounds that inhibit microbial metabolism, such as organic acids, furaldehydes, and phenolic compounds. Understanding the response of yeasts toward such inhibitors is important to the development of different bioprocesses. In this work, the growth capacity of 7 industrial Saccharomyces cerevisiae and 7 non-Saccharomyces yeasts was compared in the presence of 3 different concentrations of furaldehydes (furfural and 5-hydroxymetil-furfural), organic acids (acetic and formic acids), and phenolic compounds (vanillin, syringaldehyde, ferulic, and coumaric acids). Then, Candida tropicalis JA2, Meyerozyma caribbica JA9, Wickerhamomyces anomalus 740, S. cerevisiae JP1, B1.1, and G06 were selected for fermentation in presence of acetic acid, HMF, and vanillin because they proved to be most tolerant to the tested compounds, while Spathaspora sp. JA1 because its xylose consumption rate. The results obtained showed a dose-dependent response of the yeasts toward the eight different inhibitors. Among the compared yeasts, S. cerevisiae strains presented higher tolerance than non-Saccharomyces, 3 of them with the highest tolerance among all. Regarding the non-Saccharomyces yeasts, C. tropicalis JA2 and W. anomalus 740 appeared as the most tolerant, whereas Spathaspora strains appeared very sensitive to the different compounds.

Feeding strategies to optimize vanillin production by Amycolatopsis sp. ATCC 39116

The growing consumer demand for natural products led to an increasing interest in vanillin production by biotechnological routes. In this work, the biotechnological vanillin production by Amycolatopsis sp. ATCC 39116 is studied using ferulic acid as precursor, aiming to achieve maximized vanillin productivities. During biotech-vanillin production, the effects of glucose, vanillin and ferulic acid concentrations in the broth proved to be relevant for vanillin productivity. Concerning glucose, its presence in the broth during the production phase avoids vanillin conversion to vanillic acid and, consequently, increases vanillin production. To avoid the accumulation of vanillin up to a toxic concentration level, a multiple-pulse-feeding strategy is implemented, with intercalated vanillin removal from the broth and biomass recovery. This strategy turned out fruitful, leading to 0.46 g L^-1 h^-1 volumetric productivity of vanillin of and a production yield of 0.69 g_vanillin g_{ferulic acid}^-1, which are among the highest values reported in the literature for non-modified bacteria.

Computationally designed p-coumaric acid analogs: searching for neuroprotective antioxidants

Newly designed p-coumaric acid derivatives are promising candidates as multifunctional antioxidants with neuroprotective effects.

Effects of redox environment on hydrothermal pretreatment of lignocellulosic biomass under acidic conditions

The effects of the redox environment on acidic hydrothermal pretreatment were investigated in experiments with sugarcane bagasse (190 °C, 14 min) and Norway spruce (205 °C, 5 min). To modulate the redox environment, pretreatment was performed without gas addition, with N₂, or with O₂. Analyses covered pretreated solids, pretreatment liquids, condensates, enzymatic digestibility, and inhibitory effects of pretreatment liquids on yeast. Addition of gas, especially O₂, resulted in increased severity, as reflected by up to 18 percent units lower recoveries of pretreated solids, up to 31 percent units lower glucan recoveries, improved hemicellulose removal, formation of pseudo-lignin, improved overall glucan conversion, and increased concentrations of several microbial inhibitors. Some inhibitors, such as formaldehyde and coniferyl aldehyde, did not, however, follow that pattern. TAC (Total Aromatic Content) values reflected inhibitory effects of pretreatment liquids. This study demonstrates how gas addition can be used to modulate the severity of acidic hydrothermal pretreatment.

Variation in sugarcane biomass composition and enzymatic saccharification of leaves, internodes and roots

BACKGROUND

The composition of biomass determines its suitability for different applications within a biorefinery system. The proportion of the major biomass fractions (sugar, cellulose, hemicellulose and lignin) may vary in different sugarcane genotypes and growth environments and different parts of the plant. This study investigated the composition of mature and immature internodes, roots and mature leaves of sugarcane.

RESULTS

Internodes were found to have a significantly larger alcohol-soluble component than leaves and roots. The primary difference between the immature and mature internodes was the ratio of soluble sugars. In mature tissues, sucrose content was significantly higher, whereas in immature internodal tissues there was lower sucrose and heightened concentrations of reducing sugars. Carbon (C) partitioning in leaf tissues was characterised by low levels of soluble components and high "other" and cell wall fractions. Root tissue had low ratios of soluble fractions relative to their cell wall contents, indicating a lack of storage of soluble carbon. There was no significant difference in the ratio of the major cell wall fractions between the major organ types. Characterisation of individual non-cellulosic monomers indicated leaf and root tissues had significantly higher arabinose and galactose fractions. Significantly larger proportions of syringyl lignin compounds and the hydroxycinnamic compound, p-coumaric acid were observed in mature internodal tissues compared to the other tissue types. Tissue-specific differences in composition were shown to greatly affect the recalcitrance of the cell wall to enzymatic saccharification.

CONCLUSIONS

Overall, this study displayed clear evidence of the differential partitioning of C throughout the sugarcane plant in specific organs. These organ-specific differences have major implications in their utility as a bioproduct feedstock. For example, the inclusion of trash (leaves) with the culms (internodes) may alter processing efficiency.

Dysfunction of the 4-coumarate:coenzyme A ligase 4CL4 impacts aluminum resistance and lignin accumulation in rice

The root cell wall is the first and primary target of aluminum (Al) toxicity. Monocots such as rice (Oryza sativa) can accumulate appreciable levels of hydroxycinnamic acids (HCAs) to modify and cross-link hemicellulose and/or lignin of the cell wall. Nevertheless, it is unclear whether this HCA-mediated modification of the cell wall is important for Al accumulation and resistance. We previously isolated and characterized a rice ral1 (resistance to aluminum 1) mutant that shows enhanced Al resistance. In this study, we cloned RAL1 and found that it encodes the 4-coumarate:coenzyme A ligase 4CL4, an enzyme putatively involved in lignin biosynthesis. Mutation of RAL1/4CL4 reduces lignin content and increases the accumulation of its substrates 4-coumaric acid (PA) and ferulic acid (FA). We demonstrate that altered lignin accumulation is not required for the enhanced Al resistance in ral1/4cl4 mutants. We found that the increased accumulation of PA and FA can reduce Al binding to hemicellulose and consequently enhance Al resistance in ral1/4cl4 mutants. Al stress is able to trigger PA and FA accumulation, which is likely caused by the repression of the expression of RAL1/4CL4 and its homologous genes. Our results thus reveal that Al-induced PA and FA accumulation is actively and positively involved in Al resistance in rice through the modification of the cell wall and thereby the reduced Al binding to the cell wall.

Advances and Prospects of Phenolic Acids Production, Biorefinery and Analysis

Biotechnological production of phenolic acids is attracting increased interest due to their superior antioxidant activity, as well as other antimicrobial, dietary, and health benefits. As secondary metabolites, primarily found in plants and fungi, they are effective free radical scavengers due to the phenolic group available in their structure. Therefore, phenolic acids are widely utilised by pharmaceutical, food, cosmetic, and chemical industries. A demand for phenolic acids is mostly satisfied by utilising chemically synthesised compounds, with only a low quantity obtained from natural sources. As an alternative to chemical synthesis, environmentally friendly bio-based technologies are necessary for development in large-scale production. One of the most promising sustainable technologies is the utilisation of microbial cell factories for biosynthesis of phenolic acids. In this paper, we perform a systematic comparison of the best known natural sources of phenolic acids. The advances and prospects in the development of microbial cell factories for biosynthesis of these bioactive compounds are discussed in more detail. A special consideration is given to the modern production methods and analytics of phenolic acids.

Modulation of the human gut microbiota by phenolics and phenolic fiber-rich foods

The gut microbiota plays a prominent role in human health. Alterations in the gut microbiota are linked to the development of chronic diseases such as obesity, inflammatory bowel disease, metabolic syndrome, and certain cancers. We know that diet plays an important role to initiate, shape, and modulate the gut microbiota. Long-term dietary patterns are shown to be closely related with the gut microbiota enterotypes, specifically long-term consumption of carbohydrates (related to Prevotella abundance) or a diet rich in protein and animal fats (correlated to Bacteroides). Short-term consumption of solely animal- or plant-based diets have rapid and reproducible modulatory effects on the human gut microbiota. These alterations in microbiota profile by dietary alterations can be due to impact of different dietary macronutrients, carbohydrates, protein, and fat, which have diverse modulatory effects on gut microbial composition. Food-derived phenolics, which encompass structural variants of flavonoids, hydroxybenzoic acids, hydroxycinnamic acids, coumarins, stilbenes, ellagitannins, and lignans can modify the gut microbiota. Gut microbes have been shown to act on dietary fibers and phenolics to produce functional metabolites that contribute to gut health. Here, we discuss recent studies on the impacts of phenolics and phenolic fiber-rich foods on the human gut microbiota and provide an insight into potential synergistic roles between their bacterial metabolic products in the regulation of the intestinal microbiota.

Optimization of enzyme-assisted extraction of ferulic acid from sweet corn cob by response surface methodology

BACKGROUND

Sweet corn cob (SCC), an agricultural by-product of the corn-processing industry, contains more than 80% insoluble bound ferulic acid (FA). Extraction of these bound phenolics can be achieved through chemical or enzymatic hydrolysis; however, the shift towards greener chemistry has raised awareness about the use of enzymatic hydrolysis. In the present study, the ability of ferulic acid esterase (FAE) and xylanase (XY) to catalyze the hydrolysis of FA from SCC was investigated. Response surface methodology (RSM), based on a five-level, four-factor central composite rotatable design (CCRD), was used to establish the optimum conditions for enzymatic hydrolysis of FA from SCC. Sweet corn cob was treated with a combination of FAE and XY at various concentrations (FAE: 0.00 to 0.04 U/g; XY: 0.00 to 18 093.5 U/g), temperatures (45 to 65 °C), and pH levels (pH 4.5 to 6.5).

RESULTS

The optimum extraction conditions predicted by the model were: FAE concentration of 0.02 U/g, XY concentration of 3475.3 U/g, extraction pH of 4.5, and an extraction temperature of 45 °C.

CONCLUSION

Under these conditions, the experimental yield of FA was 1.69 ± 0.02 g kg^-1 of SCC, which is in agreement with the value predicted by the model. © 2019 Society of Chemical Industry.

Cosmetic potential of lignin extracts from alkaline-treated sugarcane bagasse: Optimization of extraction conditions using response surface methodology

Each year, sugarcane bagasse, a low-priced by-product of the sugar industry, is generated in large quantities. The aim of this study was to optimize the alkaline hydrolysis condition for the extraction of lignin from sugarcane bagasse using response surface methodology combined with Box-Behnken design, and to evaluate functional properties of lignin extracts for cosmetic applications. Three process parameters were varied (NaOH solution concentrations (3-7% w/v), temperatures (115-135 °C), and times (30-60 min)). The second-order polynomial model developed and the subsequent ANOVA test showed that the optimal conditions providing the highest total phenolic content (69.41 ± 0.32 mg gallic acid equivalent/g extract), antioxidant activity (262.30 ± 2.98 mg Trolox equivalent/g extract), and sun protection factor (8.65 ± 0.21) were as follows: NaOH solution concentration of 7% w/v, temperature of 135 °C, and time of 47.92 min. Fourier-transform infrared spectroscopy analysis revealed the functional groups present in the lignin extract that affected its activities. The extract showed both UVA and UVB-absorbing properties and tyrosinase-inhibitory properties. The results suggested that the lignin extract obtained from alkaline hydrolysis of sugarcane bagasse has great potential as a bioactive multi-functional ingredient that can offer anti-ageing, sun-protection, and skin-whitening properties for sun care formulations.

Lignocellulosic Biomass Mild Alkaline Fractionation and Resulting Extract Purification Processes: Conditions, Yields, and Purities

Fractionation of lignocellulose is a fundamental step in the valorization of cellulose, hemicelluloses, and lignin to produce various sustainable fuels, materials and chemicals. Strong alkaline fractionation is one of the most applied processes since the paper industry has been using it for more than a century, and the mineral acid fractionation process is currently the most applied for the production of cellulosic ethanol. However, in the last decade, mild alkaline fractionation has been becoming increasingly widespread in the frame of cellulosic ethanol biorefineries. It leads to the solubilization of hemicelluloses and lignin at various extent depending on the conditions of the extraction, whereas the cellulose remains insoluble. Some studies showed that the cellulose saccharification and fermentation into ethanol gave higher yields than the mineral acid fractionation process. Besides, contrary to the acid fractionation process, the mild alkaline fractionation process does not hydrolyze the sugar polymers, which can be of interest for different applications. Lignocellulosic mild alkaline extracts contain hemicelluloses, lignin oligomers, phenolic monomers, acetic acid, and inorganic salts. In order to optimize the economic efficiency of the biorefineries using a mild alkaline fractionation process, the purification of the alkaline extract to valorize its different components is of major importance. This review details the conditions used for the mild alkaline fractionation process and the purification techniques that have been carried out on the obtained hydrolysates, with a focus on the yields and purities of the different compounds.

Simultaneous production of cellulase and ferulic acid esterase by Penicillium decumbens with rice straw as the sole carbon source

As well as cellulose and hemicelluloses, rice straw contains phenolic acids. The simultaneous production of monosaccharides and phenolic acids could improve the value of rice straw. In this study, it was confirmed that Penicillium decumbens produces more ferulic acid esterase (FAE) than other cellulase-producing fungi. Cellulose, destarched wheat bran (DSWB), and rice straw were used as carbon sources. Little phenolic acid was released by cellulose- and DSWB-based enzymes during the saccharification of rice straw, whereas rice straw was a favorable carbon source for the simultaneous production of cellulase and FAE. High-performance liquid chromatography showed that during enzyme production, phenolic acids were released from rice straw, and ball-milling affected this release of phenolic acids. Small amounts of phenolic acids induced FAE production. Although the enzymes produced with rice straw showed lower FAE activity than those produced with DSWB, phenolic acids were produced efficiently during the saccharification of rice straw in response to the synergistic effects of cellulase and FAE. Therefore, we suggest that the production of enzymes by P. decumbens on rice straw as the sole carbon source will allow the production of more valuable products from rice straw, making the utilization of rice straw more economic.

A Review of Analytical Methods for p-Coumaric Acid in Plant-Based Products, Beverages, and Biological Matrices

p-Coumaric acid (p-CA), also known as 4-hydroxycinnamic acid, is a phenolic acid, which has been widely studied due to its beneficial effects against several diseases and its wide distribution in the plant kingdom. This phenolic compound can be found in the free form or conjugated with other molecules; therefore, its bioavailability and the pathways via which it is metabolized change according to its chemical structure. p-CA has potential pharmacological effects because it has high free radical scavenging, anti-inflammatory, antineoplastic, and antimicrobial activities, among other biological properties. It is therefore essential to choose the most appropriate and effective analytical method for qualitative and quantitative determination of p-CA in different matrices, such as plasma, urine, plant extracts, and drug delivery systems. The most-reported analytical method for this purpose is high-performance liquid chromatography, which is mostly coupled with some type of detectors, such as UV/Vis detector. However, other analytical techniques are also used to evaluate this compound. This review presents a summary of p-CA in terms of its chemical and pharmacokinetic properties, pharmacological effects, drug delivery systems, and the analytical methods described in the literature that are suitable for its quantification.

Improving the homogeneity of sugarcane bagasse kraft lignin through sequential solvents

The heterogeneous features of lignin, especially the wide distribution of its molecular weight, limit its high value-added application. To improve the homogeneity of lignin, sugarcane bagasse kraft lignin (KL) dissolved in methanol/acetone (7 : 3, v/v) was successively fractionated into four fractions (i.e.., F1, F2, F3, and F4) with various organic solvents of decreasing dissolving capacity (i.e.., ethyl acetate, ethyl acetate/petroleum ether 1 : 1 v/v, and petroleum ether). The yields of the four fractions (F1, F2, F3, and F4) were 59.6, 28.4, 10.8, and 1.2% that of KL, respectively. Gel permeation chromatography (GPC) analysis indicated the molecular weight of each fraction decreased from F1 to F4. All fractions had a lower polydispersity than KL. KL and the fractions were comprehensively characterized by chemical composition analysis, elemental composition analysis (EA), methoxyl group analysis, Fourier transform infrared spectroscopy (FT-IR), nitrobenzene oxidation analysis (NBO), and nuclear magnetic resonance (NMR) including ³¹P and ¹H–¹³C HSQC NMR. The results showed that the methoxyl group, hydroxyl group, interunit linkages, and thermal properties of the fractions varied with the molecular weight. The homogeneity of lignin was improved through solvent fractionation.

The heterogeneous features of lignin, especially the wide distribution of its molecular weight, limit its high value-added application.

Sugarcane cells as origin of acid beverage floc in cane sugar

Brazil stands out as the largest producer of crystal sugar in the world, exporting much of its production to the soft drinks industry. However, the chemical composition of sugar may contain numerous compounds that promote the formation of acid beverage flocs (ABF), reducing product acceptance. This study aimed to identify the chemical composition of ABF using different analytical techniques. We could observe the ABF are formed by several chemical classes. Regarding the histochemical analysis, we observed the presence of cellular sugarcane tissues, which are not fully removed in sugarcane processing. Mineral compounds, such as silicon, were found in great amounts by the Scanning electron microscopy and energy dispersive system (SEM/EDS) analysis. The mass spectrometry, high resolution mass by Q-ToF analysis and MALDI-MS allowed identification of compounds, such as p-hydroxybenzaldehyde, vanillin, triacontanoic acid, hexadecanoic acid, octadecanoic acid and n-octacosanoic acid, in the ABF composition. These compounds are widely found in vegetable tissues, confirming that the ABF are formed by tiny particles of plant cells of sugar cane.

Inhibitory effects of phenolic compounds of rice straw formed by saccharification during ethanol fermentation by Pichia stipitis

In this study, it was found that the type of phenolic acids derived from rice straw was the major factor affecting ethanol fermentation by Pichia stipitis. The aim of this study was to investigate the inhibitory effect of phenolic acids on ethanol fermentation with rice straw. Different cellulases produced different ratios of free phenolic acids to soluble conjugated phenolic acids, resulting in different fermentation efficiencies. Free phenolic acids exhibited much higher inhibitory effect than conjugated phenolic acids. The flow cytometry results indicated that the damage to cell membranes was the primary mechanism of inhibition of ethanol fermentation by phenolic acids. The removal of free phenolic acids from the hydrolysates increased ethanol productivity by 2.0-fold, indicating that the free phenolic acids would be the major inhibitors formed during saccharification. The integrated process for ethanol and phenolic acids may constitute a new strategy for the production of low-cost ethanol.

Effects of different cellulases on the release of phenolic acids from rice straw during saccharification

Effects of different cellulases on the release of phenolic acids from rice straw during saccharification were investigated in this study. All cellulases tested increased the contents of phenolic acids during saccharification. However, few free phenolic acids were detected, as they were present in conjugated form after saccharification when the cellulases from Trichoderma reesei, Trichoderma viride and Aspergillus niger were used. On the other hand, phenolic acids were present in free form when the Acremonium cellulolyticus cellulase was used. Assays of enzyme activity showed that, besides high cellulase activity, the A. cellulolyticus cellulase exhibited high feruloyl esterase (FAE) activity. A synergistic interaction between FAE and cellulase led to the increase in free phenolic acids, and thus an increase in antioxidative and antiradical activities of the phenolic acids. Moreover, a cost estimation demonstrated the feasibility of phenolic acids as value-added products to reduce the total production cost of ethanol.

The effect of non-structural components and lignin on hemicellulose extraction

As the important structural component of corn stover, hemicellulose could be converted into a variety of high value-added products. However, high quality hemicellulose extraction is not an easy issue. The present study aims to investigate the effects of non-structural components (NSCs) and lignin removal on alkaline extraction of hemicellulose. Although NSCs were found to have a minimal effect on hemicellulose dissolution, they affected the color values of the hemicellulose extracts. The lignin limited the hemicellulose dissolution and increased the color value by binding to hemicellulose molecules and forming lignin-carbohydrate complexes. Sodium chlorite method can remove about 90% lignin from corn stover, especially the lignin connected to hemicellulose through p-coumaric and ferulic acids. Which increased the hemicellulose dissolution ratio to 93% and reduced the color value 14-28%, but the cost is about 20% carbohydrates lost.

p-Coumaric acid and its conjugates: dietary sources, pharmacokinetic properties and biological activities

p-Coumaric acid (4-hydroxycinnamic acid) is a phenolic acid that has low toxicity in mice (LD50 = 2850 mg kg(-1) body weight), serves as a precursor of other phenolic compounds, and exists either in free or conjugated form in plants. Conjugates of p-coumaric acid have been extensively studied in recent years due to their bioactivities. In this review, the occurrence, bioavailability and bioaccessibility of p-coumaric acid and its conjugates with mono-, oligo- and polysaccharides, alkyl alcohols, organic acids, amine and lignin are discussed. Their biological activities, including antioxidant, anti-cancer, antimicrobial, antivirus, anti-inflammatory, antiplatelet aggregation, anxiolytic, antipyretic, analgesic, and anti-arthritis activities, and their mitigatory effects against diabetes, obesity, hyperlipaemia and gout are compared. Cumulative evidence from multiple studies indicates that conjugation of p-coumaric acid greatly strengthens its biological activities; however, the high biological activity but low absorption of its conjugates remains a puzzle. © 2015 Society of Chemical Industry.

Ferulic acid: a key component in grass lignocellulose recalcitrance to hydrolysis

In the near future, grasses must provide most of the biomass for the production of renewable fuels. However, grass cell walls are characterized by a large quantity of hydroxycinnamic acids such as ferulic and p-coumaric acids, which are thought to reduce the biomass saccharification. Ferulic acid (FA) binds to lignin, polysaccharides and structural proteins of grass cell walls cross-linking these components. A controlled reduction of FA level or of FA cross-linkages in plants of industrial interest can improve the production of cellulosic ethanol. Here, we review the biosynthesis and roles of FA in cell wall architecture and in grass biomass recalcitrance to enzyme hydrolysis.

Review on technological and scientific aspects of feruloyl esterases: A versatile enzyme for biorefining of biomass

With increasing focus on sustainable energy, bio-refining from lignocellulosic biomass has become a thrust area of research. With most of the works being focused on biofuels, significant efforts are also being directed towards other value added products. Feruloyl esterases (EC. 3.1.1.73) can be used as a tool for bio-refining of lignocellulosic material for the recovery and purification of ferulic acid and related hydroxycinnamic acids ubiquitously found in the plant cell wall. More and more genes coding for feruloyl esterases have been mined out from various sources to allow efficient enzymatic release of ferulic acid and allied hydroxycinnamic acids (HCAs) from plant-based biomass. A sum up on enzymatic extraction of HCAs and its recovery from less explored agro residual by-products is still a missing link and this review brushes up the achieved landmarks so far in this direction and also covers a detailed patent search on this biomass refining enzyme.