Birgitte K Ahring

Washington State University | WSU · Bioproducts Sciences and Engineering Laboratory

We examined the microbial populations present in fecal samples of macropods capable of utilizing a mixture of hydrogen and carbon dioxide (70:30) percent. The feces samples were cultured under anaerobic conditions, and production of methane or acetic acids characteristic for methanogenesis and homoacetogenesis was measured. While the feces of adult...

Converting corn grains into bioethanol is an expanding practice for sustainable fuel production, but this is accompanied by the production of large quantities of by-products such as whole stillage. In the present study, the influence of advanced wet oxidation and steam explosion (AWOEx) pretreatment on biogas production and lignocellulose decomposi...

A new variant of Methanothermobacter wolfeii was isolated from an anaerobic digester using enrichment cultivation in anaerobic conditions. The new isolate was taxonomically identified via 16S rRNA gene sequencing and tagged as M. wolfeii BSEL. The whole genome of the new variant was sequenced and de novo assembled. Genomic variations between the BS...

A homoacetogenic consortium was cultivated from feces from a nursing joey red kangaroo and inoculated into an in vitro ruminal culture. The in vitro ruminal culture was treated with methanogenic inhibitor 2-bromoethanesulfonate (BES), followed by two different homoacetogenic inoculation strategies. Initial observations showed inhibitory effects of...

Gasifiers produce a gaseous mixture of CO/CO2/H2, also known as synthesis gas (syngas), containing varying compositions and ratios depending on the lignocellulose material types, gasifier design, and gasification conditions. Different physicochemical and thermodynamic properties of each gas type in the various syngas blends can influence syngas fer...

The environmental impact of carbon dioxide emissions is significant, and research is focused on mitigating these emissions and developing eco-friendly technologies in line with green chemistry principles. Waste-to-energy technologies play a crucial role in converting waste into renewable energy and valuable biofuels and bioproducts. This study spec...

Biotransformation of lignocellulose-derived synthetic gas (syngas) into acetic acid is a promising way of creating biochemicals from lignocellulosic waste materials. Acetic acid has a growing market with applications within food, plastics and for upgrading into a wide range of biofuels and bio-products. In this paper, we will review the microbial c...

Fermentation of gaseous substrates such as carbon dioxide (CO2) has emerged as a sustainable approach for transforming greenhouse gas emissions into renewable fuels and biochemicals. CO2 fermentations are catalyzed by hydrogenotrophic methanogens and homoacetogens, these anaerobic microorganisms selectively reduce CO2 using hydrogen (H2) as electro...

Volatile fatty acids (VFA) are intermediary degradation products during anaerobic digestion (AD) that are subsequently converted to methanogenic substrates, such as hydrogen (H 2), carbon dioxide (CO 2), and acetic acid (CH 3 COOH). The final step of AD is the conversion of these methanogenic substrates into biogas, a mixture of methane (CH 4) and...

Methane from anaerobic fermentation in the rumen of cattle is a main contributor to greenhouse gases (50–60%). Methanogenesis is an important process in the ruminants as it scavenges hydrogen produced during the anaerobic fermentation of sugars in the rumen and, thereby, balances the fermentation process. This work focuses on mitigation of methane...

Anaerobic digestion (AD) of sewage sludge shows low carbon conversion efficiency (CCE) due to the poor biodegradability of sewage sludge. The lack of digestibility is specifically linked to the waste-activated sludge (WAS) making up the majority of sewage sludge along with a smaller portion of primary sludge, depending on the wastewater treatment p...

The anaerobic digestion of manure is facing the challenge of limited degradation because of recalcitrant nature of the fibers. In this study different concentrations (1–3%) of lime (CaO) pretreatment for AD of digested manure fibers under thermophilic conditions was evaluated. The results of the study revealed that there was 30.6, 36.4 and 23.5% re...

This study presents the effect of bioaugmentation of thermophilic anaerobic digestion of food waste with Methanosarcina thermophila grown on a wood-derived biochar. Two different supplementation regimes were tested, namely a single bioaugmentation (SBABC) in which 10% v/v of the microbes grown on biochar (1g/L) is added at setup of the reactors, ve...

Acetic acid is a valuable chemical with high demand for applications in food, pharmaceutical, polymer and other industries. A total of 10% acetate in the world is produced through bio-based processes such as fermentation. Such processes require cost-effective separation technologies to make the bio-acetate product competitive on the markets. Ion ex...

Homo-acetogens are microbes that have the ability to grow on gaseous substrates such as H2/CO2/CO and produce acetic acid as the main product of their metabolism through a metabolic process called reductive acetogenesis. These acetogens are dispersed in nature and are found to grow in various biotopes on land, water and sediments. They are also com...

Anaerobic digestion produces biogas, a mixture of CH4 and CO2, where CH4 is a low cost, environmentally friendly, and renewable energy source. The application of biogas production is increasing rapidly as a means of reducing the pollution impact of organic biomasses. However, biogas contains unwanted elements such as hydrogen sulfide, carbon monoxi...

Large amounts of lignin residue is expected in the future when biorefineries for producing biofuels and bio-products will increase in numbers. It is, therefore, valuable to find solutions for using this resource for the sustained production of useful bioenergy or bio-products. Anaerobic digestion could potentially be an option for converting the bi...

Anaerobic digestion (AD) of animal manure converts only half of the organic material into biogas due to the presence of a significant amount of lignocellulosic materials in manure. In this study, alkaline thermal pretreatment was used for improving anaerobic digestion of residual manure fibers after AD. Anaerobic digestion of pretreated manure fibe...

Food and energy requirements are increasing globally, and the challenge is to meet these demands in a sustainable manner. Oil palm has a relatively high productivity, but produces the lignocellulosic residue of empty fruit bunches (OPEFB). In this study, wet oxidation pretreatment is utilized to overcome the recalcitrance of OPEFB during semi-conti...

Volatile fatty acids (VFA) are industrially versatile chemicals and have a major market. Although currently produced from petrochemicals, chemical industries are moving towards more bio-based VFA produced from abundant, cheap and renewable sources such as lignocellulosic biomass. In this study, we examined the effect of bioaugmentation with homoace...

Anaerobic digestion of animal manure show a maximum of ca. 50% conversion of volatile solids due to recalcitrance of lignin and crystalline cellulose under anaerobic conditions. The aim of this study is to evaluate different pretreatments on anaerobic digestion of manure fibers after anaerobic digestion. Physical, chemical, thermal, and thermal com...

Palm oil production is a significant agricultural industry in the South East Asia region and the empty fruit bunch by-product OPEFB is a lignocellulosic biomass left after palm oil recovery, which has shown to be recalcitrant to bioconversion. Pretreatment experiments were carried out in this study to mitigate the recalcitrance of this material usi...

Ion-exchange resins have emerged as a promising technology for separation of targeted products from biochemical production. In this study, in-situ acetic acid extraction using Amberlite FPA53 resins was examined. The study includes initial testing of the resins for separation of different concentrations of acetic acid in water along with continuous...

The potential of leachate recirculation and enzyme addition for increasing the conversion efficiency of a 2-stage dry anaerobic digestion process of OFMSW was studied and compared to a 1- stage setup. In the 2-stage reactor setup the methane yield increased from 31 to 227 mL-CH4/g-VS by lowering waste/percolate ratio from 6.5 to 2 (based on VS). Ev...

Wet explosion pretreatment of hybrid poplar sawdust (PSD) for the production of fermentable sugar was carried out in the pilot-scale. The effects of pretreatment conditions, such as temperature (170–190 °C), oxygen dosage (0.5–7.5% of dry matter (DM), w/w), residence time (10–30 min), on cellulose and hemicellulose digestibility after enzymatic hyd...

Aspergillus carbonarius is an efficient producer of organic acids with great potential for bio-based production of organic acids. In this study, we identified a gene f2kp encoding the enzyme 6-phosphofructo-2-kinase known as an allosteric regulator of the glycolytic flux and investigated its role in the production of organic acid. The strategy was...

The increase in the generation of municipal solid waste (MSW) is a pressing challenge worldwide. Development of new management, business models, and technology paradigms to create a circular sustainable economy is among the most challenging and fascinating problems of our generation. Currently, most of the MSW around the world is processed/disposed...

This study examine ways to make biorefinery lignin accessible for anaerobic digestion. The raw material was the residue after removing carbohydrates by Wet Explosion pretreatment at 190 °C and 7.5% O2 followed by enzymatic hydrolysis. The residual solid was mainly composed of lignin and was the raw material for a second WEx pretreatment operated at...

Large-scale implementation of Biorefineries for the substitution of oil-based fuels with biofuels and bio-products will result in the production of large amounts of lignin.Furthermore,the paper and pulp industry produces lignin residues such as Kraft-lignin, which has limited use today. Lignin needs to be degraded before this high molecular weight...

Lignin, while economically and environmentally beneficial, has had limited success in use in reinforcing carbon fibers due to harmful chemicals used in biomass pretreatment along with the limited physical interactions between lignin and polyacrylonitrile (PAN) during the spinning process. The focus of this study is to use lignin obtained from chemi...

Extensive research has been done on examining the autotrophic growth of Acetobacterium woodii with gaseous substrates (hydrogen and carbon dioxide) to produce acetic acid. However, only limited work has been performed on the heterotrophic growth of A. woodii using pure sugars or lignocellulosic feedstocks-derived sugars as substrates. In this study...

Proteins, metabolites, and 16S rRNA measurements were used to examine the community structure and functional relationships within a cellulose degrading anaerobic bioreactor. The bioreactor was seeded with bovine rumen fluid and operated with a 4 day hydraulic retention time on cellulose (avicel) as sole carbon and energy source. The reactor perform...

Proteomes associated with pooled samples analagous to metagenomic libraries constructed from combining samples harvested over the span of bioreactor operation. Values within cells represent the summed spectral counts for peptides associated with each protein. (XLSX)

Bray-Curtis similarity (1—dissimilarity) between samples. Based on the VFA (top), microbial population (middle), and LC-MS feature measurements (bottom) showing redundant patterns across the different data types. Each pattern, or block, is explained by different events occurring within the bioreactor including community acclimation, established com...

Bins resulting from each metagenomic library sequenced from pooled samples collected during bioreactor operation. "Maximum Completeness" refers to the most complete assembly in the case a bin was observed within more than one library. "Cluster ID" corresponds to the clusters identified in Fig 3. (XLSX)

Pathway data associated with Fig 5. Values represent either the summed spectral count of proteins associated with a given pathway, or summed spectral counts normalized by the number of sampling events associated with a particular NMDS cluster. Cluster C2 has been parsed according to those sampling events tha occurred before the perturbation (BP) or...

Carbon balance based on 1 retention time (1.5L). (XLSX)

OTUs identified from 16s rDNA reads. Taxonomy was assigned using the RDP reference taxonomy database. Values indicate the tag count for identified OTUs. Genera in bold were also identified from metagenomic binning. Sampling dates are referenced against the time of inoculation. (XLSX)

Gas analysis results from the bioreactor headspace. CH4 and CO2 were observed during the established community; however, partial pressure for both gases dropped significantly with a rise in H2. These observed changes approximately coincide with an increase in impeller speed, suggesting an impact on syntrophic interactions. Sampling and technical di...

Measurement of fixed and volatile solids. Solids were highly variable during the period of transition to an established community. (TIF)

Microbial conversion of biomass into fatty acid-derived advanced biofuels has gained a lot of attention recently. Fatty acids and triglycerides can be used as source materials for the production of biodiesel fuel. Here, we increased internal free fatty acid and triglyceride levels in Aspergillus carbonarius, by manipulating two key enzymes of the f...

The full use of biomass in future biorefineries has stimulated studies on utilization of lignin from agricultural crops, such as coffee husk, a major residue from coffee processing. This study focuses on characterizing the lignin obtained from coffee husk and its further wet oxidation products as a function of alkali loading, temperature and reside...

Ruminal fermentation has been well studied and includes cellulolytic microorganisms to hydrolyze cellulose to monomers, acidogenic microbes including cellulolytic microorganism to convert the monomers to volatile fatty acids (VFA), hydrogen and carbon dioxide and methanogens to convert the acetic acid, hydrogen and carbon dioxide to methane. Notabl...

The wastewater stream from hydrothermal liquefaction (HTL) process used in biofuel production, contains a large amounts of organic compounds where several can be regarded as environmentally hazardous and requires significant treatment before disposal. In this study, semi-continuous anaerobic digestion is used to degrade the organic fraction of wast...

Community and technical colleges serve a vital function in STEM education by training workers for medium- and high-skilled technical careers and providing employers the labor necessary to operate and maintain thriving business ventures. A curriculum developed with the elements of a systems-based approach results in a program more relevant to the ne...

Carboxylic acids are traditionally produced from fossil fuels and have significant applications in the chemical, pharmaceutical, food, and fuel industries. Significant progress has been made in replacing such fossil fuel sources used for production of carboxylic acids with sustainable and renewable biomass resources. However, the merits and demerit...

In recent years, versatile genetic tools have been developed and applied to a number of filamentous fungi of industrial importance. However, the existing techniques have limitations when it comes to achieve the desired genetic modifications, especially for efficient gene targeting. In this study, we used Aspergillus carbonarius as a host strain due...

In this study we describe the heterologous expression of the recently identified cyanobacterial pathway for long chain alkane biosynthesis, involving the reduction of fatty acyl-ACP to fatty aldehyde and the subsequent conversion of this into alkanes, in the filamentous fungus Aspergillus carbonarius ITEM 5010. Genes originating from Synechococcus...

Volatile fatty acids (VFA) have been used as platform molecules for production of biofuels and bioproducts. In the current study, we examine the VFA production from wet-exploded corn stover through anaerobic fermentation using rumen bacteria. The total VFA yield (acetic acid equivalents) was found to increase from 22.8g/L at 2.5% total solids (TS)...

Biomass Fractionation Technologies for a Lignocellulosic Feedstock-based Biorefinery reviews the extensive research and tremendous scientific and technological developments that have occurred in the area of biorefinering, including industrial processes and product development using ‘green technologies’, often referred as white biotechnology. As the...

Aspergillus saccharolyticus exhibits great potential as a cell factory for industrial production of dicarboxylic acids. In the analysis of the organic acid profile, A. saccharolyticus was cultivated in an acid production medium using two different pH conditions. The specific activities of the enzymes, pyruvate carboxylase (PYC), malate dehydrogenas...

Significant amount of research has been done on the production of lactic acid from lignocellulosic biomass. However, most of these studies have been restricted to production using pure cultures that require expensive reactor systems operating with high sterility and clean sugar feedstocks translating into high overall processing costs. We produced...

A cost-effective K1.5Mg/SiO2 catalyst with a K2MgSiO4 component was employed to help transfer several hexoses into hydroxylmethylfurfural (HMF) in a biphasic water/butanol system. The solid catalysts with rod-like structures and moderate base sites could promote the aldose-ketose isomerization of glucose and have potential for the synthesis of lact...

Background In biorefineries, various pretreatments traditionally employ hazardous chemicals (ammonia, sulfuric acid, sulfite, etc.) for opening the softwood structure and to facilitate easy accessibility of the cellulose for further downstream processing. The resultant lignin (known as technical lignin) after extraction of the carbohydrate fraction...

The combination of catch crop cultivation with its use for biogas production would increase renewable energy production in the form of methane, without interfering with the production of food and fodder crops. The low biomass yield of catch crops has been shown as the main limiting factor for using these crops as co-substrate in biogas plants, sinc...

Lignocellulosic biomass resources especially agricultural and forests residues, perennial crops, farm wastes, and the organic fraction of municipal solid waste hold significant potential for the widespread production of sustainable fuels, chemicals and bioproducts worldwide. For biochemical conversion processes, deconstruction of lignocellulosic bi...

The filamentous fungus, Asperigillus carbonarius, is able to produce a series of hydrocarbons in liquid culture using lignocellulosic biomasses, such as corn stover and switch grass as carbon source. The hydrocarbons produced by the fungus show similarity to jet fuel composition and might have industrial application. The production of hydrocarbons...

This study investigates the effect of catch crops as co-substrate on manure-based anaerobic digestion. Batch experiments were carried out for two catch crops, namely Italian ryegrass (IR) and oil seed radish (OSR), in co-digestion with manure. Methane yields in the range of 271-558 and 216-361 ml CH4/g volatile solids (VS) were obtained for OSR and...

Catch crop biomass is a promising co-substrate for manure-based biogas plants in Denmark since the cultivation of catch crops is mandatory to retain nutrients in the soil, contributing to protect the aquatic environment. In general, the growth period for catch crops is from harvest of the previous crop in July-August to the end of the growing seaso...

A novel microorganism is provided named Aspergillus saccharolyticus. Further, beta-glucosidase enzymes encoded by said microorganism are provided, and the use thereof in the degradation of lignocellulosic material. Also, host organisms comprising the polypeptides of the invention and/or polynucleotides encoding these are provided. In addition, meth...

Integrated ‘omics have been used on pure cultures and co-cultures, yet they have not been applied to complex microbial communities to examine questions of perturbation response. In this study, we used integrated ‘omics to measure the perturbation response of a cellulose-degrading bioreactor community fed with microcrystalline cellulose (Avicel). We...

The aim of the present study was to compare bioethanol production from wet exploded corn stover (WECS) and loblolly pine (WELP) hydrolyzed with in-house and commercial enzymes and fermented separately (SHF) and simultaneously (SSF). In-house enzymes produced from Trichoderma reesei, RUT-C30 and a novel fungal strain, Aspergillus saccharolyticus wer...

Process control automation in the emerging biorefinery industry may be achieved by applying effective methods for monitoring compound concentrations during the production processes. This study examines the application of Raman spectroscopy with an excitation wavelength of 785 nm and an immersion probe for in situ monitoring the progression of pretr...