Valorizing prickly pear cladodes via methane-arrested anaerobic digestion for carboxylic acid production.

To address climate change, liquid biofuels are an essential alternative to fossil fuels, especially for transportation. The carboxylate platform uses methane-arrested anaerobic digestion (MAAD) to ferment biomass to carboxylic acids, which can be chemically converted to liquid fuels via the carboxylate platform. Most biomass sources require expensive pretreatments to remove lignin; however, prickly pear (Opuntia ficus-indica) cladodes have low lignin content and therefore do not require pretreatment.

Conversion of acetone and mixed ketones to hydrocarbons using HZSM-5 catalyst in the carboxylate platform.

In this study, two different feeds were treated to produce hydrocarbons: (1) reagent-grade acetone, and (2) mixed ketones obtained from lignocellulosic biomass via the carboxylate platform. Acetone and mixed ketones underwent catalytic self-condensation over HZSM-5. For acetone, HZSM-5(80) was used, and the experiments were conducted in two sets: (1) vary temperature (305-415°C) at P = 101 kPa (abs) and weight hourly space velocity (WHSV) = 1.

The Impact of Preservation Techniques on Methane-Arrested Anaerobic Digestion of Nutrient-Rich Feedstocks.

The carboxylate platform is a promising biomass-to-energy pathway that uses methane-arrested anaerobic digestion (MAAD) to convert biomass to carboxylic acids, which can be chemically converted to industrial chemicals and liquid fuels. Lignocellulose is an energy-rich carbon source, but lacks nutrients necessary for microbial growth. Chicken manure (rural waste) and sewage sludge (urban waste) are rich in nitrogen and useful macronutrients; therefore, co-digesting these wastes with lignocellulose improves MAAD performance.

Assessment of corn stover pretreated with shock and alkali using methane-arrested anaerobic digestion.

Corn stover, an underutilized agricultural residue, is a promising lignocellulosic feedstock for producing biofuels. To fully utilize it, pretreatment is needed. Typically, pretreatments are rapidly assessed using extracellular enzymes that release sugars from cellulose and hemicellulose.

Microbial communities for valorizing biomass using the carboxylate platform to produce volatile fatty acids: A review.

The carboxylate platform employs a diverse microbial consortium of anaerobes in which the methanogens are inhibited. Nearly all biomass components are digested to a mixture of C1-C8 monocarboxylic acids and their corresponding salts. The methane-arrested anaerobic digestion proceeds readily without needing to sterilize biomass or equipment.

Assessment of shock pretreatment and alkali pretreatment on corn stover using enzymatic hydrolysis.

This study investigates digestibility enhancements of lignocellulose from shock pretreatment, alkaline pretreatment, and combination. Shock pretreatment subjects aqueous slurries of lignocellulose to shock waves, which disrupts its structure rendering it more susceptible to hydrolysis. Alkaline pretreatment submerges the biomass in aqueous alkali (NaOH, Ca(OH) ), which removes lignin and acetyl groups.

Arrested methanogenesis digestion of high-strength cheese whey and brewery wastewater with carboxylic acid production.

A new anaerobic digestion process based on arrested methanogenesis (AM) was developed to treat high-strength cheese whey and brewery wastewater with simultaneous carboxylic acid production. This study specifically determined the links between wastewater characteristics, microbial community structure, and the operation of AM digesters at the bench scale. The highest total carboxylic acids concentration (78 g/L) was achieved after 15 days under batch condition at 40 °C and near-neutral pH.

Kinetic modeling of countercurrent saccharification.

Background: Countercurrent saccharification is a promising way to minimize enzyme loading while obtaining high conversions and product concentrations. However, in countercurrent saccharification experiments, 3-4 months are usually required to acquire a single steady-state data point. To save labor and time, simulation of this process is necessary to test various reaction conditions and determine the optimal operating point.

Development of modified HCH-1 kinetic model for long-term enzymatic cellulose hydrolysis and comparison with literature models.

Background: Enzymatic hydrolysis is a major step for cellulosic ethanol production. A thorough understanding of enzymatic hydrolysis is necessary to help design optimal conditions and economical systems. The original HCH-1 (Holtzapple-Caram-Humphrey-1) model is a generalized mechanistic model for enzymatic cellulose hydrolysis, but was previously applied only to the initial rates.

Insights into Xylan Degradation and Haloalkaline Adaptation through Whole-Genome Analysis of , an Anaerobic Haloalkaliphilic Bacterium Capable of Secreting Novel Halostable Xylanase.

The obligately anaerobic haloalkaliphilic bacterium can use xylan as the sole carbon source and produce propionate as the main fermentation product. Using mixed carbon sources of 0.4% (/) sucrose and 0.

Energy Portfolio Assessment Tool (EPAT): Sustainable energy planning using the WEF nexus approach - Texas case.

The paper introduces a holistic framework that identifies the links between energy and other systems (water, land, environment, finance, etc.), and measures the impact of energy portfolios, to offer a solid foundation for the best sustainable decision making in energy planning. The paper presents a scenario-based holistic nexus tool, Energy Portfolio Assessment Tool (EPAT) that provides a platform for energy stakeholders and policymakers to create and evaluate the sustainability of various scenarios based on the water-energy-food (WEF) nexus approach.

Draft Genome Sequence of CGMCC 1.3597, an Aerobic Haloalkaliphilic Archaeon Isolated from a Soda Lake.

The haloalkaliphilic archaeon was isolated from a soda lake in Inner Mongolia (China), growing optimally at about 20% NaCl and pH 9.0. The draft genome consists of approximately 3.

Draft Genome Sequence of DSM 18760, an Anaerobic, Halophilic, Alkaliphilic, Thermotolerant Bacterium Isolated from a Soda Lake.

The anaerobic, halophilic, alkaliphilic, thermotolerant bacterium was isolated from a soda lake in Wadi An Natrun, Egypt. It grows optimally at 3.7 M Na, pH 9.

Shock treatment of corn stover.

Corn stover digestibility was enhanced via shock treatment. A slurry of lime-treated corn stover was placed in a partially filled closed vessel. From the ullage space, either a shotgun shell was fired into the slurry, or a gas mixture was detonated.

Consolidated bioprocessing of microalgal biomass to carboxylates by a mixed culture of cow rumen bacteria using anaerobic sequencing batch reactor (ASBR).

This study employed mixed-culture consolidated bioprocessing (CBP) to digest microalgal biomass in an anaerobic sequencing batch reactor (ASBR). The primary objectives are to evaluate the impact of hydraulic residence time (HRT) on the productivity of carboxylic acids and to characterize the bacterial community. HRT affects the production rate and patterns of carboxylic acids.

Optimum alcohol concentration for chain elongation in mixed-culture fermentation of cellulosic substrate.

Medium-chain fatty acids (MCFA, e.g., caproic, heptanoic, caprylic acid) are more valuable than short-chain fatty acids (SCFA, e.

Creating Economic Incentives for Waste Disposal in Developing Countries Using the MixAlco Process.

In rapidly growing developing countries, waste disposal is a major challenge. Current waste disposal methods (e.g.

Assessment of Shock Pretreatment of Corn Stover Using the Carboxylate Platform.

Corn stover was pretreated with lime and shock, a mechanical process that uses a shockwave to alter the biomass structure. Two pretreatments (lime-only and lime + shock) were evaluated using enzymatic hydrolysis, batch mixed-culture fermentations, and continuous countercurrent mixed-culture fermentation. In a 120-h enzymatic hydrolysis, shock pretreatment increased the glucan digestibility of submerged lime pretreatment (SLP) corn stover by 3.

Evaluating the performance of carboxylate platform fermentations across diverse inocula originating as sediments from extreme environments.

To test the hypothesis that microbial communities from saline and thermal sediment environments are pre-adapted to exhibit superior fermentation performances, 501 saline and thermal samples were collected from a wide geographic range. Each sediment sample was screened as inoculum in a 30-day batch fermentation. Using multivariate statistics, the capacity of each community was assessed to determine its ability to degrade a cellulosic substrate and produce carboxylic acids in the context of the inoculum sediment chemistry.

Comparison of three screening methods to select mixed-microbial inoculum for mixed-acid fermentations.

Using a mixed culture of microorganisms, the carboxylate platform converts biomass into hydrocarbons and chemicals. To develop a method that identifies the highest performing inoculum for carboxylate fermentations, five bacterial communities were screened and ranked by three fermentation performance tests: (1) 30-day batch screen, (2) 28-day continuum particle distribution model (CPDM), and (3) 5-month continuous countercurrent fermentation trains. To screen numerous inocula sources, these tests were used sequentially in an aseptic environment.

Short-term oxidative lime pretreatment of palm pruning waste for use as animal feedstuff.

Background: Oxidative lime pretreatment (OLP) is an effective pretreatment for highly recalcitrant lignocellulosic materials. This experiment was conducted to investigate the effect of short-term OLP on fermentative gas production kinetics of date palm prunings. Rachis and petiole were pretreated with excess lime (0.

Propagated fixed-bed mixed-acid fermentation: effect of volatile solid loading rate and agitation at near-neutral pH.

To increase conversion and product concentration, mixed-acid fermentation can use a countercurrent strategy where solids and liquids pass in opposite directions through a series of fermentors. To limit the requirement for moving solids, this study employed a propagated fixed-bed fermentation, where solids were stationary and only liquid was transferred. To evaluate the role of agitation, continuous mixing was compared with periodic mixing.

Mesophilic and thermophilic conditions select for unique but highly parallel microbial communities to perform carboxylate platform biomass conversion.

The carboxylate platform is a flexible, cost-effective means of converting lignocellulosic materials into chemicals and liquid fuels. Although the platform's chemistry and engineering are well studied, relatively little is known about the mixed microbial communities underlying its conversion processes. In this study, we examined the metagenomes of two actively fermenting platform communities incubated under contrasting temperature conditions (mesophilic 40°C; thermophilic 55 °C), but utilizing the same inoculum and lignocellulosic feedstock.

Comparison of mixed-acid fermentations inoculated with six different mixed cultures.

The MixAlco™ process biologically converts biomass to carboxylate salts that may be converted to a variety of chemicals and fuels. This study examines the fermentation performance of six different mixed cultures, and how the performance was affected by the bacterial composition of each community. All six countercurrent fermentations had very similar performance, but were dissimilar in microbial community composition.

Influence of carbon-to-nitrogen ratio on the mixed-acid fermentation of wastewater sludge and pretreated bagasse.

In mixed-acid fermentation, carbon and nitrogen are critical nutrients for cell synthesis, growth, and metabolism. To study the effect of C/N ratio on the yield of carboxylic acids, wastewater sludge was co-digested with pretreated bagasse; the amount of sludge was varied from 0% to 100% (dry weight basis). Fermentation was performed at 55°C at a solids concentration of 50 g dry solids/L, and Iodoform was used to inhibit methane formation.