Cellulose Digestion Research Articles

Cello-oligosaccharides and fermentable sugars production: an integrated deacetylation-delignification process to biomass pretreatment by using a mixture of protic ionic liquids

Sugarcane straw is a residual which can be used to obtain bioproducts in a biorefinery. In this study, the pretreated biomass was used to produce both high added value products and bioenergy biomolecules from enzymatic hydrolysis by optimizing the operating conditions of the process. Cello-oligosaccharides (COS) release of 102.2mg gbiomass−1 was obtained from 6h of reaction, corresponding to a productivity of 16.6 mgCOS gbiomass−1 h−1 and a specific productivity of 3.3 mgCOS FPU−1 h−1 after pretreatment conditions optimization using mixture of ionic liquids (110 °C, 35% w w−1 water content, and 15% w w−1 [Mea][Hex]). This study also developed a one-step process integrating two important operations involved in the pretreatment of lignocellulosic biomasses named deacetylation and lignin removal. The method described can be used for fermentable sugars (cellulose digestibility of 88%) and oligosaccharides production under optimized pretreatment conditions using a mixture of protic ionic liquids with gains in productivity, cost and sustainability.

Differences in Gut Microbes Across Age and Sex Linked to Metabolism and Microbial Stability in a Hibernating Mammal.

The gut microbiome has a well-documented relationship with host fitness, physiology, and behavior. However, most of what is known comes from captive animals where diets and environments are more homogeneous or controlled. Studies in wild populations that experience dynamic environments and have natural life history variation are less common but are key to understanding the drivers of variation in the gut microbiome. Here we examine a wild population of yellow-bellied marmots (Marmota flaviventer), an obligate winter hibernator, to quantify multivariate associations between host-associated factors (e.g., age, sex, environmental harshness, and social behavior) and gut microbial composition. Across 5 years and 143 individuals, we found that males had a higher relative abundance of microbes associated with mass gain and cellulose digestion, which suggests a metabolic investment in mass gain (such as phylum Firmicutes and family Lachnospiraceae). By contrast, females had higher relative abundances of microbes associated with inflammation and metabolism (from microbial groups such as Tenericutes and Ruminococcus), possibly reflecting the importance of lactation and offspring investment. Post hoc analyses of lactating females showed a negative relationship with the abundance of microbes associated with mass gain but a positive relationship with microbes associated with metabolic energy, suggesting a trade-off between investment in pups and maternal mass gain. Older animals also had reduced Proteobacteria relative abundance, a phylum associated with reduced inflammation. Results demonstrate that sex and age-based traits, not sociality or environmental harshness, are associated with microbe-mediated metabolism and inflammation in a wild, hibernating mammal.

Assessment of the effect of browse plants’ feed formulation on Goat (<i>Capra aegagrus hircus</i>) rumen microbial activities and <i>in vitro</i> gas production

This study assessed the effect of browse Plants feed formulation on Goat (Capra aegagrus hircus) rumen microbial activities and in vitro gas production in Red Sokoto goat (Capra aegagrus hircus) over a period of fourteen (14) weeks. Four selected browse plants- Afzelia africana (TAa) Detarium microcarpum (TDm), Daniellia oliveri (TDo) and Khaya senegalensis (TKs) -were used to formulate diets for animal feeding. Three groups of growing Indigenous Red Sokoto goats were assigned to each of the browse plant diets (BPD), while the control group was placed on a basal diet only. Rumen fluids were collected from the goats intermittently for three (3) consecutive periods, and analyzed for pH, methylene blue-reduction time (MBRT), nitrate reduction, cellulose digestion, glucose fermentation and sedimentation activity rate. The results showed that browse plant feed formulation did not have a significant (p > 0.05) effect on the pH value of the rumen contents. Significant (p < 0.05) reductions in MBRT, nitrate reduction, and glucose fermentation were observed in all treatments except the control diets. However, the period for cellulose digestion significantly increased in all the browse plant-supplemented diet treatments. Furthermore, the volume of gas produced was significantly reduced by 64% (TAa), 62% (TDm), 71% (TDo), and 74% (TKs) in goats fed with browse plants as dietary supplements compared to 7% in the control (Tc). Overall, this study demonstrated that browse plant feed has the potential to significantly reduce the volume of methane produced and released by ruminant animals into the environment.

Impact of biochar on anaerobic digestion process and microbiome composition; focusing on pyrolysis conditions for biochar formation

This study is a comprehensive investigation of the role of biochar in anaerobic digestion relating various physicochemical properties and the potential biodegradability of biochar to the digestion process. Seven biochars, produced from cedar wood, wheat straw, digestate, and municipal sewage sludge, at temperatures ranging from 400 to 950 °C, were evaluated during mesophilic digestion of cellulose as a model substrate. Pyrolysis conditions significantly affected biochar's properties, with high temperatures resulting in larger surface areas (up to 1262 m2/g) and pore sizes (up to 0.7 cm3/g), more organized graphene-like structures, and higher electrical conductivities. Irrespective of the concentration and diversity of their physicochemical properties, most tested biochars did not affect methane production, despite enriching the relative abundance of the methanogenic community, even up to 42.7 %. Interestingly, wood-based biochar, post-treated by gasification at a high temperature (800 °C), reduced methane yield by up to 52 %. Contrary, methane was increased by 40 % due to residual biodegradable organic matter in biochar produced at a low temperature (400 °C) under incomplete anoxic conditions. This indicates that once the stoichiometric methane potential is reached, no additional methane can be produced by adding biochar, unless it acts as a co-substrate.

Streamlined fractionation for recovery of high-yield xylo-oligosaccharides, pure lignin and ethanol from poplar using short-chain organic acid/pentanol biphasic system

Biphasic pretreatment offers a sustainable method by integrating the fractionation of hemicellulose, lignin, and cellulose into a single process, thereby enhancing biomass resource utilization while reducing environmental impact. However, this process faces the challenge of diverse hemicellulose products with low added value. This study employed organic acid-catalyzed water/pentanol biphasic pretreatment to selectively convert hemicellulose into xylooligosaccharides (XOS), while simultaneously separating lignin and cellulose. Both the organic acids and pentanol used are biodegradable and compatible. The lactic acid (LA)/pentanol biphasic system was particularly effective for XOS production and lignin removal, attributed to the high acidity of LA and its relatively low partition coefficients in the water/pentanol system, crucial factors influencing hemicellulose and lignin separation efficiency. The XOS yields reached 46.9 %, while the lignin removal rate was 74.6 %. Additionally, LA/pentanol pretreatment significantly enhanced cellulose digestibility, demonstrated by an ethanol production of 54.1 g/L during simultaneous saccharification fermentation at 15 % solids loading. The recovered lignin from the organic phase retained the structural characteristics of native lignin. It also had a low molecular weight and abundant phenolic hydroxyl groups, indicating its suitability for further valorization. Pentanol maintained its performance after four cycles of reuse, demonstrating the stability and reusability of the solvent system. This study highlighted the potential of the LA/pentanol biphasic system for simultaneous hemicellulose conversion and lignin isolation, offering a simplified and sustainable one-step valorization route for biomass.

Variation and functional profile of gut bacteria in the scarab beetle, Anomala dimidiata, under a cellulose-enriched microenvironment

This study utilized cultivable methods and 16 S amplicon sequencing to compare taxonomic profiles and functional potential of gut bacteria in the scarab beetle, Anomola dimidiata, under cellulose-enriched conditions. Eight culturable cellulolytic gut bacteria were isolated from the midgut and hindgut of the scarab larvae, respectively. 16 S amplicon sequencing evinced that the most represented taxonomic profiles at phylum level in the fermentation chamber and midgut were Bacillota (71.62 and 56.76%), Pseudomonadota (22.66 and 36.89%) and Bacteroidota (2.7 and 2.81%). Bacillota (56.74 and 91.39%) were significantly enriched in the midgut with the addition of cellulose. In contrast, Bacillota and Psedomonadota were significantly enriched in the fermentation chamber. Carbohydrate metabolism was up-regulated in the midgut, while nitrogen and phosphorus metabolism were up-regulated in the fermentation chamber, suggesting these symbionts’ possible metabolic roles to the host. An analysis of total cellulases as well as amplicon sequence variants indicated that the gut bacteria belonging to Acinetobacter, Bacillus, Brucella, Brevibacillus, Enterobacter, Lysinibacillus and Paenibacillus are involved in nutrition provisioning. These results have provided additional insights into the gut bacteria associated with cellulose digestion in A. dimidiata and created a platform for bioprospecting novel isolates to produce biomolecules for biotechnological use, besides identifying eco-friendly targets for its management.

Optimization and characterization of a biphasic solvent system for vinegar residue pretreatment: Enhanced fractionation efficiency, propionic acid production, and sustainability

This study introduces a novel biphasic solvent system composed of phenoxyethanol and p-Toluenesulfonic acid (p-TsOH) for the pretreatment of vinegar residue (VR). The system achieves high cellulose retention (80.15 %) and effective removal of hemicellulose (97.10 %) and lignin (88.31 %) under mild conditions (127°C, 1.9 h). Structural changes in pretreated VR were analyzed, revealing significant improvements in enzymatic hydrolysis yield, achieving nearly 90 % conversion.The hydrolysate supports fermentation by Acidpropionibacterium jensenii, leading to efficient propionic acid production. The sugar-to-acid conversion rate of 28.15 % highlights the hydrolysate’s quality for lignocellulosic biotransformation. Density functional theory and molecular dynamics simulations confirm stable lignin interactions in the system, driven by hydrogen bonding, van der Waals forces, and π-π stacking, which promote lignin removal. Recycling phenoxyethanol over four cycles maintains high cellulose digestibility (84–95 %) and consistent delignification rates (88–89 %). The mass balance validated the efficient fractionation of biomass. A comprehensive analysis was conducted on the sustainability, safety, and environmental impact of the system. In conclusion, this study presents a novel biphasic solvent system that effectively fractions biomass, enhances solvent recovery, and reduces environmental impact. This system demonstrates broad applicability to different lignocellulosic biomasses, contributing to both economic and ecological sustainability.

Oil palm frond leaves (OPFLs), a high recalcitrant biomass as an alternative cellulose source for glucose conversion

Among the oil palm biomass, oil palm frond leaves (OPFLs) are under-valued since they can be classified as a high recalcitrance feedstock due to the high lignin and hemicellulose content. This work proposes a new way of using OPFLs as alternative cellulose sources for glucose conversion by an application of various pre-treatments at varying parameters. From green pre-treatment, steam explosion (SE) is much more effective in disrupting the OPFLs structure in contrast to hydrothermal (HT) pre-treatment, by a vast dissolution of hemicellulose and depolymerization of lignin. The pre-impregnation with H2SO4 prior to steam explosion was beneficial to enhance the hemicellulose removal up to 89.94 %. The 2D-HSQC NMR analysis divulged the reduction of ß-O-4 linkage and S/G value after the SE and HT pre-treatment, verifying the degradation of lignin-carbohydrate linkage in OPFLs. Meanwhile, the dilute NaOH pre-treatment enhanced the delignification by 87.14 %. SEM analysis revealed a well-disrupted structure of pre-treated OPFLs exposing a higher cellulosic fraction, whereas SEC analysis divulged a decreasing pattern of degree of polymerization of cellulose. The enzymatic analysis revealed that pre-treated OPFLs yielded higher glucose ranging from 29.81 % to 49.98 % w/w, which was ∼3-fold higher than raw OPFLs (14.31 % w/w). A maximum cellulose digestibility (100 %) was achieved by steam-exploded OPFLs after 72 h of enzymatic hydrolysis. This suggests the potency of various pre-treatments to enhance enzymatic saccharification of OPFLs producing a higher glucose yield.

DELIGNIFICATION OF OIL PALM EMPTY FRUIT BUNCHES USING DEEP EUTECTIC SOLVENT IN PRESSURIZED REACTOR

Although lignin from oil palm empty fruit bunches (OPEFB) is a sustainable bioresource with several value-added uses, it is still difficult to extract lignin from lignocellulosic biomass economically. Lignin fractions are required for high-value applications and subsequently increase the feasibility of lignocellulosic biorefineries. Besides, the remaining cellulose could be further valorized into various chemical products. In this study, the delignification efficiency of OPEFB under inert and pressurized conditions has been studied as an effective pretreatment method for OPEFB. The optimal conditions of the high-pressure reactor to remove lignin from OPEFB were determined to be 80 °C at 30 bars with the presence of deep eutectic solvents (DES). It was identified that pressure affects the removal of lignin with the least amount of structural breakdown and the digestibility of cellulose. The effective removal of lignin from the OPEFB was established under mild conditions employing an inert nitrogen gas pressurized system. This work selectively removes lignin from the OPEFB of palm oil biomass plants using DES under mild extraction conditions. Solid residues were characterized by using FTIR, SEM, TGA, and XRD to investigate fractions under various reaction conditions, such as removal temperature, time, and pressure. The thermal stability of lignin was determined by TGA. In this study, 36.68% of lignin was removed under optimum pressure conditions at the lowest process temperature of 80 °C to determine how these factors influence the efficiency of lignin extraction in a high-pressure reactor.

Comparative analysis of energy homeostasis regulation at different altitudes in Hengduan Mountain of red-backed vole, Eothenomys miletus, during high-fat diet acclimation: examining gut microbial and physiological interactions.

The study aimed to explore the similarities and differences in gut microorganisms and their functions in regulating body mass in Eothenomys miletus across different altitudes in the Hengduan Mountains when exposed to a high-fat diet. Eothenomys miletus specimens were gathered from Dali (DL) and Xianggelila (XGLL) in Yunnan Province, China, and categorized into control, high-fat (1 week of high-fat diet), and re-feeding groups (1 week of high-fat diet followed by 2 weeks of standard food). The analysis utilized 16S rRNA sequencing to assess the diversity and structure of intestinal microbial communities in E. miletus. The investigation focused on the impact of high-fat diet consumption and different altitudes on gut microbial diversity, structure, and physiological markers. Results revealed that a high-fat diet influenced the beta diversity of gut microorganisms in E. miletus, leading to variations in microbial community structure between the two regions with different altitudes. High-fat food significantly affected body mass, white adipose tissue mass, triglycerides, and leptin levels, but not food intake. Specific intestinal microorganisms were observed in the high-fat groups, aiding in food digestion and being enriched in particular flora. In particular, microbial genera like Lactobacillus and Hylemonella were enriched in the high-fat group of DL. The enriched microbiota in the control group was associated with plant polysaccharide and cellulose decomposition. Following a high-fat diet, gut microbiota adapted to support lipid metabolism and energy supply, while upon re-feeding, the focus shifted back to cellulose digestion. These findings suggested that alterations in gut microbial composition, alongside physiological markers, play a vital role in adaptation of E. miletus to the diverse habitats of the Hengduan Mountains at varying altitudes.

A Study Of Isolation And Characterisation Of Cellulolytic Bacteria For Bioethanol Production And Waste Degradation.

Cellulose is a key structural component in the cell wall of plants and a complex polysaccharide. This review delves into the diverse array of microbial Marvels that possess the enzymatic system to digest cellulose.

Buccal Swab Samples from Japanese Brown Cattle Fed with Limonite Reveal Altered Rumen Microbiome.

The areas of the Mount Aso grasslands in Kumamoto, Japan, are the primary location for the breeding of the Kumamoto strain of Japanese Brown cattle (JBRK). Although Aso limonite, deposited by volcanic ash and magma, has been commonly fed to pregnant JBRK in this area, the mechanisms of its salutary effects on pregnant JBRK have not yet been elucidated. Approximately 100 days before the expected day of calf delivery, seven JBRK (four supplemented with limonite and three controls without limonite) were assigned to this study, from which a buccal swab was collected at the highest rumination every 30 days for 90 days. DNA extracted from these swabs was then analyzed using a 16S rRNA gene amplicon sequence analysis. Statistically significant differences between the two groups were discovered through beta-diversity analysis, though results from alpha-diversity analysis were inconclusive. The microbiota identified were classified into six clusters, and three of the main clusters were core-rumen bacteria, primarily cellulose digestion in cluster 1, oral bacteria in cluster 2, and non-core-rumen bacteria in cluster 3. In the limonite group, core-rumen bacteria decreased while non-core-rumen bacteria increased, suggesting that limonite feeding alters rumen microbiota, particularly activation of non-core-rumen microbiota.

Gut microorganisms of Locusta migratoria in various life stages and its possible influence on cellulose digestibility.

Cellulose is the most abundant and cheapest renewable resource in nature, but its degradation is difficult, so finding efficient cellulose degradation methods is an urgent challenge. Locusta migratoria is a large group of agricultural pests, and the large number of microorganisms that inhabit their intestinal tracts play an important role in cellulose degradation. We analyzed the dynamics of Locusta migratoria gut microbial communities and cellulose digestibility using a combination of high-throughput sequencing technology and anthrone colorimetry. The results revealed that the gut microbial diversity and cellulose digestibility were dynamically changed at different life stages. In addition, we explored the intestinal bacterial community of Locusta migratoria across life stages and its correlation with cellulose digestibility. The dominant bacterial genera at different life stages of Locusta migratoria were uncovered and their carboxymethyl cellulase activity (CMCA) and filter paper activity (FPA) were determined. This study provides a new avenue for screening cellulolytic bacteria and lays the foundation for developing insects with significant biomass into cellulose-degrading bioreactors.

Contribution of Aerobic Cellulolytic Gut Bacteria to Cellulose Digestion in Fifteen Coastal Grapsoid Crabs Underpins Potential for Mineralization of Mangrove Production

Grapsoid crabs (Decapoda: Grapsoidea) inhabiting along the land-sea transition provided various amounts and quality of vascular plant carbon (e.g., fresh mangrove leaf, leaf litter, and mangrove-derived organic carbon) and perform differing levels of herbivory. Other than endogenous cellulase, symbiotic cellulolytic bacteria could also contribute to the crabs’ vascular plant carbon assimilation and mineralization. In this study, we isolated culturable cellulolytic bacteria from three gut regions (i.e., stomach, midgut, and hindgut) of 15 species of grapsoid crabs that inhabit in various coastal habitats (i.e., land margin, mangrove forest, tidal flat, and subtidal area). Bacillus, which was isolated from 11 out of the 15 grapsoid crabs, was the most common genus of culturable prominently cellulolytic bacteria among the target species. Seventy to ninety nine percent of culturable cellulolytic bacteria were removed, and the endoglucanase activity of five species was significantly reduced by 14.4–27.7% after antibiotic treatment. These results suggest that cellulolytic bacteria play a role in assisting mangrove carbon utilization in coastal grapsoid crabs, especially those inhabiting mangrove, mudflat, and subtidal areas. The significantly higher abundance of cellulolytic bacteria and the generally higher hydrolytic capacity of the bacteria in mangrove crab species suggest that they receive more contribution from symbionts for mangrove carbon utilization, while semi-terrestrial crabs seem to depend little on symbiotic cellulase due to the lower abundances.

Exploration and origin studies of high levels of β-glucosidase in carnivorous fishes spotted knifejaw (Oplegnathus punctatus)

In order to more efficiently utilize the abundant cellulose resources in nature, increase the utilization rate of cellulose in aquaculture, implement precise feeding and save aquaculture costs, we have conducted research on cellulase genes related to the spotted knifejaw (Oplegnathus punctatus). Cellulose, as the most abundant renewable resource, is a cornerstone in the intricate ecological balance of diverse ecosystems. While herbivorous fish are recognized for their utilization of proteins, sugars, and fats, the extent of cellulose utilization by carnivorous and omnivorous fish remains an enigma. Here, through field sampling and behavioural observations, O. punctatus' omnivorous diet has been demonstrated (stomach contents contain approximately several species of algae in the Bacillariophyta (1.12 %), Streptomyces (0.55 %), Chlorophyta (0.35 %), Rhodophyta (0.16 %), and Euglenophyta (0.19 %) phylum). Additionally, the high cellulase activity in the intestine of O. punctatus has been detected first discovery (enzyme activity up to 4800.15 U/g), indicating its ability to digest cellulose. By employing whole-genome scanning and high-throughput sequencing, a single cellulase gene (β-glucosidase) within the genome of O. punctatus, suggesting the absence of a complete cellulose digestive system. However, microbiological analysis revealed the three crucial role of microorganisms, including Actinobacteria (25.80 %), Bacteroidetes (18.93 %), and Firmicutes phylum (0.82 %), were found to play a crucial role in the decomposition of plant cell walls, thereby facilitating plant material digestion to help the host to complete the process of cellulose digestion. Expression patterns and proteomic analysis of the β-glucosidase were notably high in the gonads. In situ hybridization confirmed the expression of the β-glucosidase gene in the intestinal contents and gonads, highlighting its role in supplying energy of gonads. These discoveries shed light on the dietary habits of O. punctatus and its cellulose utilization, offering insights that can inform the development of customized feeding strategies to enhance aquaculture sustainability and minimize resource expenditure.

Assessment of deep eutectic solvents (DES) to fractionate Paulownia wood within a biorefinery scheme: Cellulosic bioethanol production and lignin isolation

Five deep eutectic solvents (DES) were evaluated to disrupt Paulownia wood structure to produce bioethanol and lignin. The DES formulated with choline chloride:lactic acid provided the most promising result. Temperature (110–130 °C), residence time (30–120 min), molar ratio (1:2–1:9), and liquid-to-solid ratio (8–15 mL/g) were optimized for cellulose recuperation (93% retained in the solid phase) and lignin removal (94% delignification yield). The spent solid was used for bioethanol production, achieving up to 43.6 g ethanol/L (89.7% ethanol yield). Lignin (84% of purity) was isolated from the black liquor and thoroughly characterized by FTIR, 1H NMR, TGA-DTG and SEM, while the liquor after lignin precipitation was chemically characterized for monomers/oligomers, total phenolic content, antioxidant activity and phytochemical profile (highlighting the presence of 25.06, 10.21 and 2.51 mg of syringaldehyde, vanillin and 3,4-dihydroxibenzoic acid per g of initial biomass). Overall, this study show that DES pre-treatment is a promising strategy for simultaneous lignin extraction and cellulose digestibility enhancement.

A study revealing mechanisms behind the stone cell of Yali pear degradation by mixed‐culture fermentation of lactic acid bacteria and yeast

AbstractThe presence of stone cells in pears is recognized as a problem for the pear processing industry. Bacillus and mold can degrade stone cells because of their potential to digest cellulose and lignin, but they cannot be used for the degradation test of pear stone cells. In this study Lactoplantibacillus plantarum JYLP‐326 was used in single culture or in the mixed culture with Saccharomyces cerevisiae Y2 to study their potential to degrade stone cells during fermentation and the mechanism of degradation was further explored. Synergy in cellulase activity was observed in the mixed‐culture where the maximum activity was observed at 96th hour of fermentation. Activities of endoglucanase, exoglucanase and β‐glucosidase were 1.75, 4.58, and 2.31. The degradation rate of stone cells in the mixed‐culture was 37.67%, which was significantly higher than that the results obtained for single cultures. The results of scanning electron microscopy (SEM) showed that the surface of the cultured stone cells became rough. Metabolomics studies confirmed the presence of specific metabolites related to the degradation of stone cells after the fermentation. It was concluded that the mixed‐culture fermentation using the above‐mentioned strains could be exploited by the pear processing industry to degrade stone cells.

Ultrasound Assisted Pre-treatments for the Efficient And Sustainable Conversion of Biomass Into Biofuels

The growing focus on sustainable and efficient biomass-to-biofuels conversion, driven by environmentalconcerns and the demand for eco-friendly processes has become a key area of research. Biomass, a vitalrenewable energy source, harbors the potential for direct transformation into liquid biofuels such as ethanoland biodiesel, signifying a noteworthy progression in biofuel technology. Persistent challenges, includingsuboptimal biofuel yields and heightened production costs arise from incomplete cellulose digestion shieldedby lignin. In response, various pretreatment methods have been investigated to augment cellulose andhemicellulose accessibility by disrupting lignin cross-links. Among these strategies, ultrasonic irradiation orsonication emerges as a promising eco-friendly pretreatment for the efficient conversion of lignocellulosicbiomass into biofuels.This article explores the prerequisites of effective pretreatments, highlighting the significance of dualapplication, minimal energy consumption, the use of economically viable chemicals, and consideration ofmoderate temperatures and pressures. By delving into the mechanism of ultrasound irradiation, the studyelucidates how ultrasound waves generate cavitation bubbles, initiating both physical and chemicaltransformations in biomass. In-depth discussions encompass factors influencing sonication, includingduration, frequency, power, temperature, liquid medium, and suspended solids. Critical considerations foroptimizing pretreatment efficiency are outlined in the design aspects of sonochemical reactors, coveringreactor configuration, ultrasonic frequency, power dissipation, duration, and temperature. The articleconcludes by underscoring the evolving potential of ultrasound-assisted pretreatments in biofuel productionand encourages further detailed advancements and comprehensive studies to actualize their full-scaleindustrial applications.

Stormwater runoff microplastics: Polymer types, particle size, and factors controlling loading rates

Stormwater runoff is a pathway of entry for microplastics (MPs, plastics <5 mm) into aquatic ecosystems. The objectives of this study were to determine MP size, morphology, chemical composition, and loading across urban storm events. Particles were extracted from stormwater samples collected at outfall locations using wet peroxide oxidation and cellulose digestion followed by analysis via attenuated total reflectance (ATR) FTIR. Concentrations observed were 0.99 ± 1.10 MP/L for 500–1000 μm and 0.41 ± 0.30 MP/L for the 1000–5000 μm size ranges. Seventeen different polymer types were observed. MP particle sizes measured using a FTIR-microscope camera indicated non-target size particles based on sieve-size classification, highlighting a potential source of error in studies reporting concentration by size class. A maximum MP load of 38.3 MP/m2 of upstream catchment was calculated. MP loadings had moderate correlations with both rainfall accumulation and intensity (Kendall τ = 0.54 and 0.42, respectively, both p ≤ 0.005). First flush (i.e. rapid wash-off of pollutants from watershed surfaces during rainfall early stages) was not always observed, and antecedent dry days were not correlated with MP abundance, likely due to the short dry periods between sampling events. Overall, the results presented provide data for risk assessment and mitigation strategies.

Cryptic diversity of cellulose-degrading gut bacteria in industrialized humans.

Humans, like all mammals, depend on the gut microbiome for digestion of cellulose, the main component of plant fiber. However, evidence for cellulose fermentation in the human gut is scarce. We have identified ruminococcal species in the gut microbiota of human populations that assemble functional multienzymatic cellulosome structures capable of degrading plant cell wall polysaccharides. One of these species, which is strongly associated with humans, likely originated in the ruminant gut and was subsequently transferred to the human gut, potentially during domestication where it underwent diversification and diet-related adaptation through the acquisition of genes from other gut microbes. Collectively, these species are abundant and widespread among ancient humans, hunter-gatherers, and rural populations but are rare in populations from industrialized societies thus indicating potential disappearance in response to the westernized lifestyle.