Persistent action of cow rumen microorganisms in enhancing biodegradation of wheat straw by rumen fermentation

Lycium barbarum (Wolfberry) Branches and Leaves Enhance the Growth Performance and Improve the Rumen Microbiota in Hu Sheep

The Lycium barbarum branches and leaves (LBL) are known to contain a range of active substances that have positive effects on animal immunity and antioxidation. This study aimed to examine how LBL impacts the growth and slaughter performance as well as rumen fermentation and microbiota in Hu sheep. A total of 50 male Hu sheep of indigenous origin, aged 3 months, were randomly divided into 5 groups of 10 sheep each. The groups were given different levels of LBL supplementation (0%, 3%, 6%, 9%, and 12%) to evaluate growth performance and nutrient apparent digestibility. Rumen fluid samples were collected for analysis of the fermentation parameters and rumen chyme was examined to study the rumen microbiota. The slaughter performance, meat quality, and organ index were evaluated at the conclusion of the experiment. The results showed that the final body weight and average daily gain of the LBL1 group were significantly higher than those of the CON group, LBL3 group, and LBL4 group (p < 0.05). The average dry matter intake of the LBL4 group was significantly lower than that of other experimental groups (p < 0.05). The apparent digestibility of CP in the LBL1 and LBL2 groups was higher than that in other experimental groups (p < 0.05). At the same time, the eye muscle area and grade-rule (GR) value of Hu sheep in the LBL1 group significantly increased and the quality of Hu sheep meat improved (p < 0.05). There was no significant difference in organ weight and organ index between the experimental groups (p > 0.05). The pH of the rumen fluid in the LBL1 group was significantly lower than that in the CON group (p < 0.05). There was no significant difference in the NH3-N content between the experimental groups (p > 0.05). The propionate and valerate in the rumen fluid of Hu sheep in the LBL2 group were significantly higher than those in other experimental groups (p < 0.05). In addition, this had no significant effect on the structure and abundance of the rumen microbiota (p > 0.05). LBL is a promising functional feed. Adding an appropriate amount of LBL to the diet can improve the feed efficiency, growth performance, and meat quality of Hu sheep but has no adverse effects on the rumen. In this experiment, the appropriate supplemental level of LBL in the diet was 3%.

Application of microbial resources in biorefineries: Current trend and future prospects

The recent growing interest in sustainable and alternative sources of energy and bio-based products has driven the paradigm shift to an integrated model termed "biorefinery." Biorefinery framework implements the concepts of novel eco-technologies and eco-efficient processes for the sustainable production of energy and value-added biomolecules. The utilization of microbial resources for the production of various value-added products has been documented in the literatures. However, the appointment of these microbial resources in integrated resource management requires a better understanding of their status. The main of aim of this review is to provide an overview on the defined positioning and overall contribution of the microbial resources, i.e., algae, fungi and bacteria, for various bioprocesses and generation of multiple products from a single biorefinery. By utilizing waste material as a feedstock, biofuels can be generated by microalgae while sequestering environmental carbon and producing value added compounds as by-products. In parallel, fungal biorefineries are prolific producers of lignocellulose degrading enzymes along with pharmaceutically important novel products. Conversely, bacterial biorefineries emerge as a preferred platform for the transformation of standard cells into proficient bio-factories, developing chassis and turbo cells for enhanced target compound production. This comprehensive review is poised to offer an intricate exploration of the current trends, obstacles, and prospective pathways of microbial biorefineries, for the development of future biorefineries.

Rumen fermentation and microbial diversity of sheep fed a high-concentrate diet supplemented with hydroethanolic extract of walnut green husks

OBJECTIVE

This study aimed to assess the impact of a hydroethanolic extract of walnut green husks (WGH) on rumen fermentation and the diversity of bacteria, methanogenic archaea, and fungi in sheep fed a high-concentrate diet.

METHODS

Five healthy small-tailed Han ewes with permanent rumen fistula were selected and housed in individual pens. This study adopted a self-controlled and crossover design with a control period and an experimental period. During the control period, the animals were fed a basal diet (with a ratio of concentrate to roughage of 65:35), while during the treatment period, the animals were fed the basal diet supplemented with 0.5% hydroethanolic extract of WGH. Fermentation parameters, digestive enzyme activities, and microbial diversity in rumen fluid were analyzed.

RESULTS

Supplementation of hydroethanolic extract of WGH had no significant effect on feed intake, concentrations of total volatile fatty acids, isovalerate, ammonia nitrogen, and microbial protein (p>0.05). However, the ruminal pH, concentrations of acetate, butyrate and isobutyrate, the ratio of acetate to propionate, protozoa count, and the activities of filter paper cellulase and cellobiase were significantly increased (p<0.05), while concentrations of propionate and valerate were significantly decreased (p<0.05). Moreover, 16S rRNA gene sequencing revealed that the relative abundance of rumen bacteria Christensenellaceae R7 group, Saccharofermentans, and Ruminococcaceae NK4A214 group were significantly increased, while Ruminococcus gauvreauii group, Prevotella 7 were significantly decreased (p<0.05). The relative abundance of the fungus Pseudomonas significantly increased, while Basidiomycota, Fusarium, and Alternaria significantly decreased (p<0.05). However, there was no significant change in the community structure of methanogenic archaea.

CONCLUSION

Supplementation of hydroethanolic extract of WGH to a high-concentrate diet improved the ruminal fermentation, altered the structure of ruminal bacterial and fungal communities, and exhibited beneficial effects in alleviating subacute rumen acidosis of sheep.

Rumen microbes, enzymes, metabolisms, and application in lignocellulosic waste conversion - A comprehensive review

The rumen of ruminants is a natural anaerobic fermentation system that efficiently degrades lignocellulosic biomass and mainly depends on synergistic interactions between multiple microbes and their secreted enzymes. Ruminal microbes have been employed as biomass waste converters and are receiving increasing attention because of their degradation performance. To explore the application of ruminal microbes and their secreted enzymes in biomass waste, a comprehensive understanding of these processes is required. Based on the degradation capacity and mechanism of ruminal microbes and their secreted lignocellulose enzymes, this review concentrates on elucidating the main enzymatic strategies that ruminal microbes use for lignocellulose degradation, focusing mainly on polysaccharide metabolism-related gene loci and cellulosomes. Hydrolysis, acidification, methanogenesis, interspecific H2 transfer, and urea cycling in ruminal metabolism are also discussed. Finally, we review the research progress on the conversion of biomass waste into biofuels (bioethanol, biohydrogen, and biomethane) and value-added chemicals (organic acids) by ruminal microbes. This review aims to provide new ideas and methods for ruminal microbe and enzyme applications, biomass waste conversion, and global energy shortage alleviation.

Microbial diversity in dairy manure environment under liquid-solid separation systems

In dairy manure, a wide array of microorganisms, including many pathogens, survive and grow under suitable conditions. This microbial community offers a tremendous opportunity for studying animal health, the transport of microbes into the soil, air, and water, and consequential impacts on public health. The aim of this study was to assess the impacts of manure management practices on the microbial community of manure. The key novelty of this work is to identify the impacts of various stages of manure management on microbes living in dairy manure. In general, the majority of dairy farms in California use a flush system to manage dairy manure, which involves liquid-solid separations. To separate liquid and solid in manure, Multi-stage Alternate Dairy Effluent Management Systems (ADEMS) that use mechanical separation systems (MSS) or weeping wall separation systems (WWSS) are used. Thus, this study was conducted to understand how these manure management systems affect the microbial community. We studied the microbial communities in the WWSS and MSS separation systems, as well as in the four stages of the ADEMS. The 16S rRNA gene from the extracted genomic DNA of dairy manure was amplified using the NovoSeq Illumina next-generation sequencing platform. The sequencing data were used to perform the analysis of similarity (ANOSIM) and multi-response permutation procedure (MRRP) statistical tests, and the results showed that microbial communities among WWSS and MSS were significantly different (p < 0.05). These findings have significant practical implications for the design and implementation of manure management practices in dairy farms.

Diet and monensin influence the temporal dynamics of the rumen microbiome in stocker and finishing cattle

BACKGROUND

Stocker cattle diet and management influence beef cattle performance during the finishing stage, but knowledge of the dynamics of the rumen microbiome associated with the host are lacking. A longitudinal study was conducted to determine how the feeding strategy from the stocker to the finishing stages of production affects the temporal dynamics of rumen microbiota. During the stocker phase, either dry hay or wheat pasture were provided, and three levels of monensin were administrated. All calves were then transported to a feedlot and received similar finishing diets with or without monensin. Rumen microbial samples were collected on d 0, 28, 85 during the stocker stage (S0, S28 and S85) and d 0, 14, 28, 56, 30 d before slaughter and the end of the trial during the finishing stage (F0, F14, F28, F56, Pre-Ba, and Final). The V4 region of the bacterial 16S rRNA gene of 263 rumen samples was sequenced.

RESULTS

Higher alpha diversity, including the number of observed bacterial features and the Shannon index, was observed in the stocker phase compared to the finishing phase. The bacterial amplicon sequence variants (ASVs) differentiating different sampling time points were identified. Dietary treatments during the stocker stage temporally impact the dynamics of rumen microbiota. For example, shared bacteria, including Bacteroidales (ASV19) and Streptococcus infantarius (ASV94), were significantly higher in hay rumen on S28, S85, and F0, while Bacteroidaceae (ASV11) and Limivicinus (ASV15) were more abundant in wheat. Monensin affected rumen microbial composition at a specific time. Transportation to feedlot significantly influenced microbiome structure and diversity in hay-fed calves. Bacterial taxa associated with body weight were classified, and core microbiotas interacted with each other during the trial.

CONCLUSIONS

In summary, the temporal dynamics of the rumen microbiome in cattle at the stocker and finishing stage are influenced by multiple factors of the feeding strategy. Diet at the stocker phase may temporarily affect the microbial composition during this stage. Modulating the rumen microbiome in the steers at the stocker stage affects the microbial interactions and performance in the finishing stage.

Simulating Rumen Conditions Using an Anaerobic Dynamic Membrane Bioreactor to Enhance Hydrolysis of Lignocellulosic Biomass

An anaerobic dynamic membrane bioreactor (AnDMBR) mimicking rumen conditions was developed to enhance the hydrolysis of lignocellulosic materials and the production of volatile fatty acids (VFAs) when treating food waste. The AnDMBR was inoculated with cow rumen content and operated at a 0.5 day hydraulic retention time, 2-4 day solids retention time, a temperature of 39 °C, and a pH of 6.3, characteristics similar to those of a rumen. Removal rates of neutral detergent fiber and acid detergent fiber of 58.9 ± 8.4 and 69.0 ± 8.6%, respectively, and a VFA yield of 0.55 ± 0.12 g VFA as chemical oxygen demand g volatile solids (VS)fed-1 were observed at an organic loading rate of 18 ± 2 kg VS m-3 day-1. The composition and activity of the microbial community remained consistent after biofilm disruption, bioreactor upset, and reinoculation. Up to 66.7 ± 5.7% of the active microbial populations and 51.0 ± 7.0% of the total microbial populations present in the rumen-mimicking AnDMBR originated from the inoculum. This study offers a strategy to leverage the features of a rumen; the AnDMBR achieved high hydrolysis and fermentation rates even when treating substrates different from those fed to ruminants.

From transients to permanent residents: the existence of obligate aerobic microorganisms in the goat rumen

The rumen serves as a complex ecosystem, harboring diverse microbial communities that play crucial ecological roles. Because previous studies have predominantly focused on anaerobic microorganisms, limited attention has been given to aerobic microorganisms in the goat rumen. This study aims to explore the diversity of aerobic microorganisms in the rumen and understand their niche and ecological roles. Rumen fluid samples were collected from 6 goats at different time points post-morning feeding. pH, NH3-N, and volatile fatty acid (TVFA) concentrations were measured, while In vitro cultivation of aerobic microorganisms was performed using PDA medium. Internal Transcribed Spacer (ITS) and 16S sequencing unveiled microbial diversity within the rumen fluid samples. Evidence of obligate aerobic microorganisms in the goat rumen suggests their potential contribution to ecological functionalities. Significantly, certain aerobic microorganisms exhibited correlations with TVFA levels, implying their involvement in TVFA metabolism. This study provides evidence of the existence and potential ecological roles of obligate aerobic microorganisms in the goat rumen. The findings underscore the significance of comprehensively deciphering goat rumen microbial communities and their interactions, with aerobes regarded as permanent residents rather than transients. These insights form a solid foundation for advancing our understanding of the intricate interplay between goat and their aerobic microorganisms in the rumen.

Microbial composition play the leading role in volatile fatty acid production in the fermentation of different scale of corn stover with rumen fluid

Rumen fluid is a natural and green biocatalyst that can efficiently degrade biomass into volatile fatty acid (VFA) used to produce value-added materials. But the essence of high degradation efficiency in the rumen has not been fully analyzed. This study investigated the contribution of substrate structure and microbial composition to volatile fatty acid production in the fermentation of corn stover. The ball milled corn stover were innovatively applied to ferment with the rumen fluid collected at different digestion times. Exogeneous cellulase was also added to the ruminal fermentation to further reveal the inner mechanism. With prolonged digestion time, the microbial community relative abundance levels of Bacteroidetes and Firmicutes increased from 29.98% to 72.74% and decreased from 51.76% to 22.11%, respectively. The highest VFA production of the corn stover was achieved via treatment with the rumen fluid collected at 24 h which was up to 9508 mg/L. The ball milled corn stover achieved high VFA production because of the more accessible substrate structure. The application of exogenous cellulase has no significant influence to the ruminal fermentation. The microbial community abundance contributed more to the VFA production compared with the substrate structures.

A Glycosyl Hydrolase 30 Family Xylanase from the Rumen Metagenome and Its Effects on In Vitro Ruminal Fermentation of Wheat Straw

The challenge of wheat straw as a ruminant feed is its low ruminal digestibility. This study investigated the impact of a xylanase called RuXyn, derived from the rumen metagenome of beef cattle, on the in vitro ruminal fermentation of wheat straw. RuXyn encoded 505 amino acids and was categorized within subfamily 8 of the glycosyl hydrolase 30 family. RuXyn was heterologously expressed in Escherichia coli and displayed its highest level of activity at pH 6.0 and 40 °C. RuXyn primarily hydrolyzed xylan, while it did not show any noticeable activity towards other substrates, including carboxymethylcellulose and Avicel. At concentrations of 5 mM, Mn2+ and dithiothreitol significantly enhanced RuXyn's activity by 73% and 20%, respectively. RuXyn's activity was almost or completely inactivated in the presence of Cu2+, even at low concentrations. The main hydrolysis products of corncob xylan by RuXyn were xylopentose, xylotriose, and xylotetraose. RuXyn hydrolyzed wheat straw and rice straw more effectively than it did other agricultural by-products. A remarkable synergistic effect was observed between RuXyn and a cellulase cocktail on wheat straw hydrolysis. Supplementation with RuXyn increased dry matter digestibility; acetate, propionate, valerate, and total volatile fatty acid yields; NH3-N concentration, and total bacterial number during in vitro fermentation of wheat straw relative to the control. RuXyn's inactivity at 60 °C and 70 °C was remedied by mutating proline 151 to phenylalanine and aspartic acid 204 to leucine, boosting activity to 20.3% and 21.8% of the maximum activity at the respective temperatures. As an exogenous enzyme preparation, RuXyn exhibits considerable potential to improve ruminal digestion and the utilization of wheat straw in ruminants. As far as we know, this is the first study on a GH30 xylanase promoting the ruminal fermentation of agricultural straws. The findings demonstrate that the utilization of RuXyn can significantly enhance the ruminal digestibility of wheat straw by approximately 10 percentage points. This outcome signifies the emergence of a novel and highly efficient enzyme preparation that holds promise for the effective utilization of wheat straw, a by-product of crop production, in ruminants.

Effect of Dietary and Age Changes on Ruminal Microbial Diversity in Holstein Calves

Ruminal microorganisms play a crucial role in the energy supply of ruminants and animal performance. We analyzed the variations in rumen bacteria and fungi at 45 d, 75 d, and 105 d by using 16SrRNA and ITS sequencing data and investigated their correlation with rumen fermentation. According to the results, rumen microflora tended to gradually mature with age, and bacterial and fungal establishment gradually stabilized. Upon comparing the three periods, the concentration of propionic acid increased significantly (p < 0.05) after weaning, and weaning accompanied by a transition in diet remarkably decreased (p < 0.05) rumen diversity in the short term and induced a corresponding change in the rumen microbiota composition. Bacteroidota, Actinobacteriota, and Firmicutes were the core bacterial phyla for all age periods. Ruminococcus, NK4A214_group, Sharpea, Rikenellaceae_RC9_gut_group, and norank_f__Butyricicoccaceae were the markedly abundant bacterial genera in pre-weaning. After weaning, the relative abundance of Erysipelotrichaceae_ UCG-002, Eubacterium_ruminantium_group, and Solobacterium significantly increased (p < 0.05). The relative abundance of Acetitomaculum increased with age with the greatest abundance noted at 105 d (37%). The dominant fungal phyla were Ascomycota and Basidiomycota, and Aspergillus and Xeromyces were the most abundant fungal genera after weaning. Trichomonascus, Phialosimplex, and Talaromyces were enriched at 105 d. However, the low abundance of Neocallimastigomycota was not detected throughout the study, which is worthy of further investigation. In addition, correlations were observed between age-related abundances of specific genera and microbiota functions and rumen fermentation-related parameters. This study revealed that rumen microbiota and rumen fermentation capacity are correlated, which contributed to a better understanding of the effects of age and diet on rumen microbiology and fermentation in calves.

Differences in composition and diversity of rumen fungi in buffalo fed different diets

The rumen is a complex ecosystem containing a variety of fungi, which are crucial for the digestive activities of ruminants. Previous research on rumen fungi has mainly focused on anaerobic fungi, given the rumen's reputation as a mainly anaerobic environment. The objective of this study was to investigate rumen fungal diversity and the presence of aerobic fungi in buffalo fed on different diets. Three adult buffaloes were used as experimental animals. Alfalfa hay, oat hay, whole corn silage, sugarcane shoot silage, fresh king grass, dried rice straw, and five kinds of mixed diets with concentrate to roughage ratios of 20:80, 35:65, 50:50, 65:35, and 80:20 were used as the experimental diets. The experimental animals were fed different diets for 22 days. Rumen fluid was collected from the rumen fistula for ITS (Internal Transcribed Spacer) sequencing 2 h after feeding on the morning of day 22. The results indicate the presence of large quantities of aerobic fungi in the rumen of the buffaloes 2 h after feeding and suggest that Ascomycota and Basidiomycota are the dominant fungal groups under different feeding conditions. The study also identified 62 different fungal types, which showed significant differences among the 11 experimental diets.

Insight into the differences of meat quality between Qinghai white Tibetan sheep and black Tibetan sheep from the perspective of metabolomics and rumen microbiota

The purpose of this study was to investigate the differences in meat quality between two local breeds of Tibetan sheep, the White Tibetan sheep and the Black Tibetan sheep in Qinghai, and to search for metabolic mechanisms that produce meat quality differences by analyzing differential metabolites and key rumen microorganisms. The meat quality results showed that one breed, SG73, was superior to the other (WG). Further investigation identified differences in the composition of muscle metabolites and rumen microorganisms between the two Tibetan sheep breeds. It also regulates muscle tenderness, water retention, fat content and the composition and content of AA and FA through two major metabolic pathways, AA metabolism and carbohydrate metabolism. These findings could be beneficial for the development of breeding strategies for Tibetan sheep in Qinghai in the future.

Long-term in-situ starvation and reactivation of co-digestion with food waste and corn straw in a continuous AnDMBR: Performance, sludge characteristics, and microorganism community

To explore the effects of in-situ starvation and reactivation in a continuous anaerobic dynamic membrane reactor (AnDMBR), the anaerobic co-digestion system of food waste and corn straw was firstly start-up and stability operated, and then stopped feeding substrate approximately 70 days. After long-term in-situ starvation, the continuous AnDMBR was reactivated using the same operation conditions and organic loading rate as the continuous AnDMBR used before in-situ starvation. Results shown that the anaerobic co-digestion of corn straw and food waste in the continuous AnDMBR can resume stable operation within 5 days, and the corresponding methane production of 1.38 ± 0.26 L/L/d was completely returned to the methane production before in-situ starvation (1.32 ± 0.10 L/L/d). Through analysis of the specific methanogenic activity and key enzyme activity of the digestate sludge, only the acetic acid degradation activity of methanogenic archaea can be partially recovered, however, the activities of lignocellulose enzyme (lignin peroxidase, laccase, and endoglucanase), hydrolase (α-glucosidase) and acidogenic enzyme (acetate kinas, butyrate kinase, and CoA-transferase) can be fully recovered. Analysis of microorganism community structure using metagenomic sequencing technology showed that starvation decreased the abundance of hydrolytic bacteria (Bacteroidetes and Firmicutes) and increased the abundance of small molecule-utilizing bacteria (Proteobacteria and Chloroflexi) due to lack of substrate during the long-term in-situ starvation stage. Furthermore, the microbial community structure and key functional microorganism still maintained and similar with that of starvation final stage even after long-term continuous reactivation. The reactor performance and sludge enzymes activity in the continuous AnDMBR co-digestion of food waste and corn straw can be well reactivated after long-term in-situ starvation, even though the microbial community structure can not be recovered to the initiating stage.

Metagenomic analysis reveals the efficient digestion mechanism of corn stover in Angus bull rumen: Microbial community succession, CAZyme composition and functional gene expression

Ruminant rumen is a biological fermentation system that can efficiently degrade lignocellulosic biomass. The knowledge about mechanisms of efficient lignocellulose degradation with rumen microorganisms is still limited. In this study, composition and succession of bacteria and fungi, carbohydrate-active enzymes (CAZymes), and functional genes involved in hydrolysis and acidogenesis were revealed during fermentation in Angus bull rumen via metagenomic sequencing. Results showed that degradation efficiency of hemicellulose and cellulose reached 61.2% and 50.4% at 72 h fermentation, respectively. Main bacterial genera were composed of Prevotella, Butyrivibrio, Ruminococcus, Eubacterium, and Fibrobacter, and main fungal genera were composed of Piromyces, Neocallimastix, Anaeromyces, Aspergillus, and Orpinomyces. Principal coordinates analysis indicated that community structure of bacteria and fungi dynamically changed during 72 h fermentation. Bacterial networks with higher complexity had stronger stability than fungal networks. Most CAZyme families showed a significant decrease trend after 48 h fermentation. Functional genes related to hydrolysis decreased at 72 h, while functional genes involved in acidogenesis did not change significantly. These findings provide a in-depth understanding of mechanisms of lignocellulose degradation in Angus bull rumen, and may guide the construction and enrichment of rumen microorganisms in anaerobic fermentation of waste biomass.

Effect of organic amendments obtained from different pretreatment technologies on soil microbial community

The application of organic amendments (OAs) obtained from biological treatment technologies is a common agricultural practice to increase soil functionality and fertility. OAs and their respective pretreatment processes have been extensively studied. However, comparing the properties of OAs obtained from different pretreatment processes remains challenging. In most cases, the organic residues used to produce OAs exhibit intrinsic variability and differ in origin and composition. In addition, few studies have focused on comparing OAs from different pretreatment processes in the soil microbiome, and the extent to which OAs affect the soil microbial community remains unclear. This limits the design and implementation of effective pretreatments aimed at reusing organic residues and facilitating sustainable agricultural practices. In this study, we used the same model residues to produce OAs to enable meaningful comparisons among compost, digestate, and ferment. These three OAs contained different microbial communities. Compost had higher bacterial but lower fungal alpha diversity than ferment and digestate. Compost-associated microbes were more prevalent in the soil than ferment- and digestate-associated microbes. More than 80% of the bacterial ASVs and fungal OTUs from the compost were detected 3 months after incorporation into the soil. However, the addition of compost had less influence on the resulting soil microbial biomass and community composition than the addition of ferment or digestate. Specific native soil microbes, members from Chloroflexi, Acidobacteria, and Mortierellomycota, were absent after ferment and digestate application. The addition of OAs increased the soil pH, particularly in the compost-amended soil, whereas the addition of digestate enhanced the concentrations of dissolved organic carbon (DOC) and available nutrients (such as ammonium and potassium). These physicochemical variables were key factors that influenced soil microbial communities. This study furthers our understanding of the effective recycling of organic resources for the development of sustainable soils.

Characterization of bovine ruminal content focusing on energetic potential use and valorization opportunities

This work characterized the bovine ruminal content excluding stomach tissue obtained from a slaughterhouse plant located in Cordoba, Colombia. The goal is to establish possible energetic uses and valorization potential instead of risky local current contaminant practices. Samples of ruminal content (RC) were collected under two conditions as-fresh and dry. Microbiological and bromatological quality, density, proximate and elemental analysis, and calorific power values were measured. There were complemented with optical microscopy, SEM, XEDS, FTIR, TGA, and TGA-MS analysis for both conditions. Ashes of combustion products from mixtures of natural gas and RC were studied, using XRD and XRF techniques. Results showed that fresh-state RC has an important microbiological quality without some human risk pathogens, such as Salmonella sp, E. coli, and vegetable risk pathogens, such as nematodes. Dry and sieved state RC is lignin-cellulosic heterogeneous biomass, with a real density of 164 kg/m³, a calorific power between 12 and 15 kJ/kg, and ashes rich in alkaline-earth elements. These results indicate that RC might have a good potential in co-combustion, gasification, and other energy processes. However, important considerations should be done about management of RC, because its direct application as fertilizer could carry out a negative effect, which was demonstratred in the growth of a model plant.

Sulphonated graphene catalyst incorporation with sludge enhanced the microbial activities for biomethanization of crude rice straw

Biomethanization of crude rice straw (RS) was enhanced by a coupled effectiveness of sulphonated graphene (SGR) with sludge rich anaerobes (SRA). A reduction of 19.2 ± 1.32% for cellulose, 40.8 ± 3.7% for hemicellulose and 30.8 ± 2.4% for lignin was achieved with addition of SRA after fermentation of 60 days. The abundance of hydrolytic microbes in SRA i.e. Acidobacteria, Bacteroidetes, Chloroflexi and Proteobacteria caused RS structure liquefaction and dissolution. The reduction of cellulose, hemicellulose and lignin boosted to 92.3 ± 1.5, 84.9 ± 3.5 and 97.0 ± 1.8% respectively with SGR catalyst addition of 100 mg/gVS. Reducing sugars, phenols and volatile fatty acids (VFAs) were subsequently utilized by bacteria and archaea species of Methanosphaera, Methanocella, Candidatus Methanoregula, Methanolinea and Methanosaeta. The biogas yield was 92 ± 3.1 mL/gRS and methane content amounted to 68 ± 4.6% % at SGR catalyst of 80 mg/gVS. These findings show the potential of using SRA/SGR to improve the RS fermentation with a novel application for biogas productivity.

Wheat supplement with buckwheat affect gut microbiome composition and circulate short-chain fatty acids

Buckwheat has beneficial effects on human intestinal health, which is often compounded with wheat to make food. Therefore, the effect of cereals mixture via in vitro fermentation on gut microbes and short-chain fatty acids (SCFAs) were investigated in this study. The mixture of wheat and tartary buckwheat (WT) produced more lactate and acetate, and the mixture of wheat and sweet buckwheat (WE) produced more propionate and butyrate. Compared with wheat (WA), the relative abundance of some beneficial bacteria significantly increased, such as Sutterella in WT and Faecalibacterium in WE. Cereals mixture also affected the expression of functional genes, involved in metabolic pathways and carbohydrate-active enzymes (CAZymes) that modulated SCFAs generation. This study provides new insights into the effects of sweet and tartary buckwheat on intestinal function, which is beneficial to applying both types of buckwheat in practical.

Improving production of lactic acid and volatile fatty acids from dairy cattle manure and corn straw silage: Effects of mixing ratios and temperature

Anaerobic co-fermentation (AcoF) of dairy cattle manure (DCM) and corn straw silage (CSS) for producing lactic acid (LA) and volatile fatty acids (VFAs) was investigated. Batch experiments were conducted at seven different DCM/CSS ratios and at mesophilic and thermophilic temperatures. Results indicated that the highest concentration of LA was 17.50 ± 0.70 g/L at DCM:CSS ratio of 1:3 and thermophilic temperature, while VFAs was 18.23 ± 2.45 g/L at mono-CSS fermentation and mesophilic temperature. High solubilization of thermophilic conditions contributed to LA accumulation in AcoF process. Presence of the CSS increased the relative abundance of Lactobacillus for LA production at thermophilic. Meanwhile, the abundance of Bifidobacterium was increased when CSS was added at mesophilic, which could conduce to VFAs production. This study provides a new route for enhancing the biotransformation of DCM and CSS into short-chain fatty acids, potentially bringing economic benefits to agricultural waste treatment.

Long-term rumen microorganism fermentation of corn stover in vitro for volatile fatty acid production

Rumen microorganisms have the ability to efficiently hydrolyze and acidify lignocellulosic biomass. The effectiveness of long-term rumen microorganism fermentation of lignocellulose in vitro for producing volatile fatty acids (VFAs) is unclear. The feasibility of long-term rumen microorganism fermentation of lignocelluose was evaluated in this study, and a stable VFA production was successfully realized for 120 d. Results showed that VFA concentration reached to 5.32-8.48 g/L during long-term fermentation. Hydrolysis efficiency of hemicellulose and cellulose reached 36.5%-52.2% and 29.4%-38.4%, respectively. A stable bacterial community was mainly composed of Prevotella, Rikenellaceae_RC9_gut_group, Ruminococcus, and Succiniclasticum. VFA accumulation led to a pH decrease, which caused the change of bacterial community structure. Functional prediction showed that the functional genes related to hydrolysis and acidogenesis of corn stover were highly expressed during long-term fermentation. The successful long-term rumen fermentation to produce VFAs is of great significance for the practical application of rumen microorganisms.

Effects of residual monensin in livestock manure on nitrogen transformation and microbial community during "crop straw feeding-substrate fermentation-mushroom cultivation" recycling system

Although crop-livestock integration recycling systems improve nitrogen (N) utilization in agroecosystems, there are limited studies regarding impacts of residual antibiotics in livestock manure on N transformation in entire recycling system. The objective was to evaluate effects of feeding monensin on N recycling during "straw feeding-substrate fermentation-mushroom cultivation". This experiment contained 3 steps. During straw feeding, beef cattle were allocated into 2 groups and fed diets with or without monensin, respectively. During fermentation, beef cattle manure (with or without monensin) and straw (corn or wheat) and were co-fermented for 35 d to produce substrates. During cultivation, Agaricus bisporus was cultivated on 4 substrates to recycle N in the form of mushrooms. Rates of N retention during fermentation were significant higher for monensin and corn straw treatments and there was an significant interaction between straw and antibiotic on N retention rate during cultivation. However, residual monensin significantly reduced amount of recycled N during entire recycling system, due to changes in N transformation-associated enzyme activity, ammonification and denitrification plus microbial community structure and succession. Specifically, residual monensin inhibited growth of dominant bacterial phylum Bacteroidetes and fungal phylum Neocallimastigomycota, and increased bacterial phylla Actinobacteriota and Firmicutes. These alterations in functional microbes increased N retention rates but reduced mushroom yields in antibiotic treatments during cultivation. In conclusion, monensin decreased the N recycling rate in recycling system, but also reduced N losses during fermentation by inhibiting ammonification and denitrification, so, avoiding antibiotics usage is an effective strategy to improve the efficiency of recycling systems.

Current Progress in Optimising Sustainable Energy Recovery From Cattle Paunch Contents, a Slaughterhouse Waste Product

Paunch contents are the recalcitrant, lignocellulose-rich, partially-digested feed present in the rumen of ruminant animals. Cattle forage in Europe is primarily from perennial and Italian ryegrasses and/or white clover, so paunch contents from forage-fed cattle in Europe is enriched in these feedstuffs. Globally, due to its underutilisation, the potential energy in cattle paunch contents annually represents an energy loss of 23,216,548,750–27,804,250,000 Megajoules (MJ) and financial loss of up to ~€800,000,000. Therefore, this review aims to describe progress made to-date in optimising sustainable energy recovery from paunch contents. Furthermore, analyses to determine the economic feasibility/potential of recovering sustainable energy from paunch contents was carried out. The primary method used to recover sustainable energy from paunch contents to-date has involved biomethane production through anaerobic digestion (AD). The major bottleneck in its utilisation through AD is its recalcitrance, resulting in build-up of fibrous material. Pre-treatments partially degrade the lignocellulose in lignocellulose-rich wastes, reducing their recalcitrance. Enzyme systems could be inexpensive and more environmentally compatible than conventional solvent pre-treatments. A potential source of enzyme systems is the rumen microbiome, whose efficiency in lignocellulose degradation is attracting significant research interest. Therefore, the application of rumen fluid (liquid derived from dewatering of paunch contents) to improve biomethane production from AD of lignocellulosic wastes is included in this review. Analysis of a study where rumen fluid was used to pre-treat paper sludge from a paper mill prior to AD for biomethane production suggested economic feasibility for CHP combustion, with potential savings of ~€11,000 annually. Meta-genomic studies of bacterial/archaeal populations have been carried out to understand their ruminal functions. However, despite their importance in degrading lignocellulose in nature, rumen fungi remain comparatively under-investigated. Further investigation of rumen microbes, their cultivation and their enzyme systems, and the role of rumen fluid in degrading lignocellulosic wastes, could provide efficient pre-treatments and co-digestion strategies to maximise biomethane yield from a range of lignocellulosic wastes. This review describes current progress in optimising sustainable energy recovery from paunch contents, and the potential of rumen fluid as a pre-treatment and co-substrate to recover sustainable energy from lignocellulosic wastes using AD.

Effect of microwave/hydrothermal combined ionic liquid pretreatment on straw: Rumen anaerobic fermentation and enzyme hydrolysis

To explore green technology for wheat straw pretreatment, this study combined the microwave or hydrothermal with ionic liquid ([Bmim][OAc]) on wheat straw followed by rumen fermentation. The optimal conditions of microwave assisted ionic liquids pretreatment (M-I) and hydrothermal assisted ionic liquids pretreatment (H-I) treatment were 360 W and 200 °C, and the corresponding lignin removal rates reached 35.3% and 25.4%, respectively. Rumen fermentation showed that the highest volatile fatty acid (VFA) yield was found in M-I group, followed by H-I group at 234 and 180 mg/g, respectively. As for enzymatic hydrolysis, the saccharification rates at 3 days of M-I (360 W) and H-I (200 °C) were determined to be 393 and 320 mg/g. The optimal ionic liquid dosage was determined to be 30% in consideration of cost and VFA conversion rate. M-I pretreatment plus the rumen fermentation enjoyed the benefit of no enzyme addition and high product recovery, which was worth further investigating.

Biotechnological potential of rumen microbiota for sustainable bioconversion of lignocellulosic waste to biofuels and value-added products

Lignocellulosic biomass is an abundant resource with untapped potential for biofuel, enzymes, and chemical production. Its complex recalcitrant structure obstructs its bioconversion into biofuels and other value-added products. For improving its bioconversion efficiency, it is important to deconstruct its complex structure. In natural systems like rumen, diverse microbial communities carry out hydrolysis, acidogenesis, acetogenesis, and methanogenesis of lignocellulosic biomass through physical penetration, synergistic and enzymatic actions enhancing lignocellulose degradation activity. This review article aims to discuss comprehensively the rumen microbial ecosystem, their interactions, enzyme production, and applications for efficient bioconversion of lignocellulosic waste to biofuels. Furthermore, meta 'omics' approaches to elucidate the structure and functions of rumen microorganisms, fermentation mechanisms, microbe-microbe interactions, and host-microbe interactions have been discussed thoroughly. Additionally, feed additives' role in improving ruminal fermentation efficiency and reducing environmental nitrogen losses has been discussed. Finally, the current status of rumen microbiota applications and future perspectives for the development of rumen mimic bioreactors for efficient bioconversion of lignocellulosic wastes to biofuels and chemicals have been highlighted.

Translational multi-omics microbiome research for strategies to improve cattle production and health

Cattle microbiome plays a vital role in cattle growth and performance and affects many economically important traits such as feed efficiency, milk/meat yield and quality, methane emission, immunity and health. To date, most cattle microbiome research has focused on metataxonomic and metagenomic characterization to reveal who are there and what they may do, preventing the determination of the active functional dynamics in vivo and their causal relationships with the traits. Therefore, there is an urgent need to combine other advanced omics approaches to improve microbiome analysis to determine their mode of actions and host-microbiome interactions in vivo. This review will critically discuss the current multi-omics microbiome research in beef and dairy cattle, aiming to provide insights on how the information generated can be applied to future strategies to improve production efficiency, health and welfare, and environment-friendliness in cattle production through microbiome manipulations.

Ensiling pretreatment with two novel microbial consortia enhances bioethanol production in sterile rice straw

The present study extracts and enriches cellulolytic microbial consortia from yak (Bos grunniens) and evaluates their effects on the fermentation profile and bioethanol yield in rice straw silage. Two microbial consortia (CF and PY) with high cellulolytic activity were isolated and observed to be prone to utilize natural carbon sources. Two consortia were introduced with and without combined lactic acid bacteria (CLAB) to rice straw for up to 60 days of ensiling, and their application notably decreased the levels of structural carbohydrates and pH values of rice straw silages. Treatments that combining microbial consortia and CLAB resulted in the highest levels of lactic acid, water soluble carbohydrates, mono- and disaccharides, and lignocellulose degradation, with PY + CLAB group yielding the highest bioethanol production. The microbial consortia identified herein exhibit great potential for degrading fibrous substrates, and their combination with CLAB provides a feasible way to efficiently use rice straw for bioethanol production.

Characterization and identification of a novel microbial consortium M2 and its effect on fermentation quality and enzymatic hydrolysis of sterile rice straw

AIMS

To isolate and enrich lignocellulolytic microbial consortia from yak (Bos grunniens) rumen and evaluate their effects on the fermentation characteristics and enzymatic hydrolysis in rice straw silage.

METHODS AND RESULTS

A novel microbial consortium M2 with high CMCase and xylanase activities was enriched and observed to be prone to use natural carbon sources. Its predominant genus was Enterococcus, and most carbohydrate-active enzyme (CAZyme) genes belonged to the glycosyl hydrolases class. The consortium M2 was introduced with or without combined lactic acid bacteria (XA) to rice straw silage for 60 days. Inoculating the consortium M2 notably decreased the structural carbohydrate contents and pH of rice straw silages. Treatment that combines consortium M2 and XA resulted in the highest levels of lactic acid and lignocellulose degradation. The consortium M2 alone or combined with XA significantly (p < 0.01) increased water-soluble carbohydrates (WSCs), mono- and disaccharides contents compared with the XA silage. Combined addition obviously improved the enzymatic conversion efficiency of rice straw silage with higher glucose and xylose yields (23.39 and 12.91 w/w% DM, respectively).

CONCLUSIONS

Ensiling pretreatment with the microbial consortium M2 in sterile rice straw improved fermentation characteristics. The combined application of consortium M2 with XA had synergistic effects on promoting the degradation of structural carbohydrates and enzymatic hydrolysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Rice straw is difficult to ensile because of its low WSC and high structural carbohydrate contents. The microbial consortium M2 identified herein exhibits great potential for degrading fibrous substrates, and their combination with XA provides a faster and more effective synergistic strategy for biorefinery of lignocellulosic biomass.

A Review on Bacterial Contribution to Lignocellulose Breakdown into Useful Bio-Products

Discovering novel bacterial strains might be the link to unlocking the value in lignocellulosic bio-refinery as we strive to find alternative and cleaner sources of energy. Bacteria display promise in lignocellulolytic breakdown because of their innate ability to adapt and grow under both optimum and extreme conditions. This versatility of bacterial strains is being harnessed, with qualities like adapting to various temperature, aero tolerance, and nutrient availability driving the use of bacteria in bio-refinery studies. Their flexible nature holds exciting promise in biotechnology, but despite recent pointers to a greener edge in the pretreatment of lignocellulose biomass and lignocellulose-driven bioconversion to value-added products, the cost of adoption and subsequent scaling up industrially still pose challenges to their adoption. However, recent studies have seen the use of co-culture, co-digestion, and bioengineering to overcome identified setbacks to using bacterial strains to breakdown lignocellulose into its major polymers and then to useful products ranging from ethanol, enzymes, biodiesel, bioflocculants, and many others. In this review, research on bacteria involved in lignocellulose breakdown is reviewed and summarized to provide background for further research. Future perspectives are explored as bacteria have a role to play in the adoption of greener energy alternatives using lignocellulosic biomass.

Caproicibacterium amylolyticum gen. nov., sp. nov., a novel member of the family Oscillospiraceae isolated from pit clay used for making Chinese strong aroma-type liquor

An anaerobic, Gram-stain-positive, rod-shaped, motile and spore-forming bacterium, designated strain LBM18003^T, was isolated from pit clay used for making Chinese strong aroma-type liquor. Growth occurred at 20-40 °C (optimum, 30-37 °C), pH 4.5-9.5 (optimum, pH 6.5-7.0) and in the presence of 0.0-1.0 % (w/v) sodium chloride (optimum, 0 %). The predominant fatty acids were C_16:0, C_14:0, C_14:0 DMA and C_16:0 3-OH, and the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two unidentified phospholipids and nine unidentified glycolipids. Phylogenetic analysis revealed that strain LBM18003^T is a novel member of the family Oscillospiraceae. The 16S rRNA gene sequence similarities of strain LBM18003^T to its two most closely related species were less than 94.5 % for distinguishing genera, i.e. closely related to Caproiciproducens galactitolivorans JCM 30532^T (94.1 %) and Caproicibacter fermentans DSM 107079^T (93.2 %). The genome size of strain LBM18003^T was 2 996 201 bp and its DNA G+C content was 48.48 mol%. Strain LBM18003^T exhibited 67.8 and 68.1% pairwise-determined whole-genome average nucleotide identity values to Caproiciproducens galactitolivorans JCM 30532^T and Caproicibacter fermentans DSM 107079^T, respectively; and showed 62.2 and 61.0 % the average amino acid identity values to Caproiciproducens galactitolivorans JCM 30532^T and Caproicibacter fermentans DSM 107079^T, respectively; and demonstrated 46.1 and 41.5 % conserved genes to Caproiciproducens galactitolivorans JCM 30532^T and Caproicibacter fermentans DSM 107079^T, respectively. The comparisons of 16S rRNA gene and genome sequences confirmed that strain LBM18003^T represented a novel genus of the family Oscillospiraceae. Based on morphological, physiological, biochemical, chemotaxonomic, genotypic and phylogenetic results, strain LBM18003^T represents a novel species of a novel genus of the family Oscillospiraceae, for which the name Caproicibacterium amylolyticum gen. nov., sp. nov. is proposed. The type strain is LBM18003^T (=GDMCC 1.1626^T=JCM 33783^T).

Effect of microaerobic microbial pretreatment on anaerobic digestion of a lignocellulosic substrate under controlled pH conditions

The effects of various microaeration strategies and process parameters on anaerobic digestion (AD) of lignocellulosic substrates have received increased attention; however, different results have been reported. To determine optimal conditions and clarify the mechanisms influencing this process, the effect of pretreatment of microaerobic microbial on corn stover decomposition and AD was investigated with real-time pH control. Fresh cow manure was chosen as the inoculum, as it has the strongest cellulose hydrolysis capacity under microaeration conditions. Microaeration microbial pretreatment effectively promoted the hydrolysis and acidogenesis of corn stover, and pH considerably affected total solid reduction, volatile fatty acid (VFA), and accumulation of soluble chemical oxygen demand (sCOD) patterns by shifting microbial communities. Different pH levels and pretreatment times led to positive and negative effects on methane yield. A 12-h pretreatment of substrate at pH 8 prior to AD increased the methane yield by 16.6% in comparison with the un-pretreated sample.

Effect of substrate load on anaerobic fermentation of rice straw with rumen liquid as inoculum: Hydrolysis and acidogenesis efficiency, enzymatic activities and rumen bacterial community structure

Rumen liquid is excellent to effectively degrade lignocellulose. In this study, the suitable rice straw load during anaerobic fermentation of rice straw with rumen liquid as inoculum was explored to improve volatile fatty acid (VFA) production. At 10.0% rice straw load, the highest VFA concentration reached 10821.4 mg/L, and acetic acid and propionic acid were the main components. In 10.0% rice straw load system, high concentration of soluble chemical oxygen demand (SCOD) was also observed, and the enzymatic activities at 48 h were higher than those at other rice straw loads. At 10.0% rice straw load, lower diversity and richness of rumen bacteria were found than those at other rice straw loads. Bacteroides, Prevotella, and Ruminococcus were the main rumen bacteria during rice straw degradation, and the rumen bacteria might secret effective lignocellulolytic enzymes to enhance the hydrolysis and acidogenesis of rice straw. The determination of suitable rice straw load will be beneficial to the application of rumen liquid as inoculum in actual production.

Transformation of bacterial community structure in rumen liquid anaerobic digestion of rice straw

Rumen liquid can effectively degrade lignocellulosic biomass, in which rumen microorganisms play an important role. In this study, transformation of bacterial community structure in rumen liquid anaerobic digestion of rice straw was explored. Results showed that rice straw was efficiently hydrolyzed and acidified, and the degradation efficiency of cellulose, hemicellulose and lignin reached 46.2%, 60.4%, and 12.9%, respectively. The concentration of soluble chemical oxygen demand (SCOD) and total volatile fatty acid (VFA) reached 12.9 and 8.04 g L^-1. The high-throughput sequencing results showed that structure of rumen bacterial community significantly changed in anaerobic digestion. The Shannon diversity index showed that rumen bacterial diversity decreased by 32.8% on the 5th day of anaerobic digestion. The relative abundance of Prevotella and Fibrobacter significantly increased, while Ruminococcus significantly decreased at the genus level. The Spearman correlation heatmap showed that pH and VFA were the critical factors affecting the rumen bacterial community structure. The function prediction found that rumen bacteria mainly functioned in carbohydrate transport and metabolism, which might contain a large number of lignocellulose degrading enzyme genes. These studies are conducive to the better application of rumen microorganisms in the degradation of lignocellulosic biomass.

A comparative study of artificial cow and sheep rumen fermentation of corn straw and food waste: Batch and continuous operation

To optimize the artificial rumen microorganism sources and develop a stable artificial rumen system, batch and continuous operation were investigated with corn straw and food waste as substrates. The batch trials evaluated the volatile fatty acid (VFA) yield, biogas production, and lignocellulose degradation efficiency. The continuous test evaluated the performance of the artificial cow and sheep rumen systems using a dynamic membrane bioreactor (DMBR) with a stepwise organic loading rate at mesophilic temperature. The anaerobic digestion (AD) of the lignocellulose biomass after rumen fermentation pretreatment and of the permeate from the artificial rumen system were also evaluated for CH₄ production. The results indicated that the cow rumen microorganisms were more suitable than sheep rumen microorganisms for lignocellulosic biomass pretreatment and maximized the CH₄ yield through the AD process without inhibition. After approximately four months of continuous operation, a stable and continuous artificial rumen system for lignocellulosic biomass degradation was achieved with cow rumen fluid as inoculum. Based on analysis of the core lignocellulose-degrading enzyme levels and gel filtration chromatography, the cow rumen microorganisms could secrete more extracellular multienzyme complexes to hydrolyze lignocellulosic biomass than the sheep rumen microorganisms in vitro. During the batch and continuous operations, a high diversity and similar richness of bacteria and fungi demonstrated that the cow rumen microorganisms can be used as a preferred inoculum for the artificial rumen system. The use of an artificial cow rumen system with a DMBR is a promising way to construct a stable and continuous artificial rumen system to biodegrade lignocellulosic biomass for biogas production.

Acclimatization of anaerobic sludge with cow manure and realization of high-rate food waste digestion for biogas production

Long-term acclimatization of anaerobic sludge was conducted by operating a mesophilic continuously stirred anaerobic reactor (CSTR) with continuous feeding of food wastes (FW) and cow manure (CM). During the long-term acclimatization, continued increase of enzyme activity was revealed, while the microbial structure tended stable as shown by the Shannon index and microbial community. By biomethane potential analysis, the acclimated sludge had a methane yield about 13 times higher than the initial anaerobic sludge. The acclimated sludge was subsequently used for FW digestion with stepwise organic loading rate increase without CM addition. The functional phyla of Bacteroidetes and Proteobacteria, which originated from CM but not very abundant, were significantly enriched not only during sludge acclimatization with CM addition but also in the process of FW digestion without CM addition. A microbe coexistence network was proposed to support an explanation of the metabolic pathways of FW digestion using the acclimated sludge.

Microorganisms and Enzymes Used in the Biological Pretreatment of the Substrate to Enhance Biogas Production: A Review

The pretreatment of lignocellulosic biomass (LC biomass) prior to the anaerobic digestion (AD) process is a mandatory step to improve feedstock biodegradability and biogas production. An important potential is provided by lignocellulosic materials since lignocellulose represents a major source for biogas production, thus contributing to the environmental sustainability. The main limitation of LC biomass for use is its resistant structure. Lately, biological pretreatment (BP) gained popularity because they are eco-friendly methods that do not require chemical or energy input. A large number of bacteria and fungi possess great ability to convert high molecular weight compounds from the substrate into lower mass compounds due to the synthesis of microbial extracellular enzymes. Microbial strains isolated from various sources are used singly or in combination to break down the recalcitrant polymeric structures and thus increase biogasgeneration. Enzymatic treatment of LC biomass depends mainly on enzymes like hemicellulases and cellulases generated by microorganisms. The articles main purpose is to provide an overview regarding the enzymatic/biological pretreatment as one of the most potent techniques for enhancing biogas production.

Cosubstrate strategy for enhancing lignocellulose degradation during rumen fermentation in vitro: Characteristics and microorganism composition

To enhance the degradation of wheat straw (WS) and corn straw (CS) in rumen fermentation, characterization of degradation and ruminal microorganisms of monosubstrate (WS/CS) groups and a cosubstrate strategy with food waste (FW) group was performed. The cellulose, hemicellulose, and lignin degradation efficiency of WS and CS; soluble chemical oxygen demand; volatile fatty acid yields; and activity of ligninolytic, cellulolytic, and hemicellulolytic enzymes for the cosubstrate group were improved compared with those for the corresponding monosubstrate groups. An accurate and a good of fit of the Weibull kinetic model, decreased crystallinity index values, and characteristic absorbance bands in the Fourier transform-infrared spectra further confirmed that cosubstrate addition with FW decreased the resistance of cellulose and hemicellulose to biodegradation. High-throughput sequencing results suggested that the bacterial diversity in CS rumen fermentation and fungal diversity and richness in WS rumen fermentation were promoted with FW as a cosubstrate. The cosubstrate addition with FW significantly affected the composition of the ruminal bacteria and fungi in rumen fermentation. The relative abundances (RAs) of rumen bacteria were increased in the cosubstrate CS/WS and FW fermentation conditions, and the enhancement of CS degradation with FW supplementation was stronger than that of WS rumen fermentation with FW supplementation. The RAs of the ruminal fungal genera Ustilago and Fusarium were promoted in CS and WS fermentation with FW, respectively. Moreover, the fermentation properties and rumen flora in the FW rumen fermentation also provided some evidence to suggest an enhancement of the cosubstrate strategy compared with the monosubstrate strategy.

Determination of Various Parameters during Thermal and Biological Pretreatment of Waste Materials

Pretreatment of waste materials could help in more efficient waste management. Various pretreatment methods exist, each one having its own advantages and disadvantages. Moreover, a certain pretreatment technique might be efficient and economical for one feedstock while not for another. Thus, it is important to analyze how parameters change during pretreatment. In this study, two different pretreatment techniques were applied: thermal at lower and higher temperatures (38.6 °C and 80 °C) and biological, using cattle rumen fluid at ruminal temperature (≈38.6 °C). Two different feedstock materials were chosen: sewage sludge and riverbank grass (Typha latifolia), and their combinations (in a ratio of 1:1) were also analyzed. Various parameters were analyzed in the liquid phase before and after pretreatment, and in the gas phase after pretreatment. In the liquid phase, some of the parameters that are relevant to water quality were measured, while in the gas phase composition of biogas was measured. The results showed that most of the parameters significantly changed during pretreatments and that lower temperature thermal and/or biological treatment of grass and sludge is suggested for further applications.