Analysis of the beryllium stability under standard and critical operation in a fusion reactor

Currently, dark fermentation is the most practically applicable for the implementation of biotechnological roduction of hydrogen. However, this process has certain limiting factors, since a significant part of the substrates are converted into various metabolic products, but not into H2 . Therefore, it is necessary to develop optimal conditions for energy recovery in the form of gaseous molecular hydrogen. Various carbohydrate-containing raw materials for hydrogen production often require pretreatment before they can be used by microorganisms. Dilute acid pretreatment represents a promising way to increase biohydrogen production. However, during acid hydrolysis of carbohydrate-containing wastes, in addition to the released soluble sugars, inhibitors of enzymatic processing, such as furfural and 5-HMF, acetic and propionic acids, etc., can accumulate. In this regard, it is necessary to select the optimal conditions for the efficient production of biohydrogen. This study investigated the production of biohydrogen during the microbial fermentation of sugars in a dilute solution of a molasses-based acid hydrolyzate using Escherichia coli and a multiple mutant. The results of the experiments showed that molasses is a valuable product as a source of carbon and energy for microorganisms in the production of biohydrogen, as well as for the production of biomass for the further production of various products with high added value.

Mathematical model of steady-state countercurrent bed-shrinking reactor in dilute acid

The mathematical model of bed-shrinking in a countercurrent reactor proposed by Lee (Bioresource Technology 71 (2000) 29 - 39) is explored. This model is based on system of nonlinear differential equations. Analytically, the coupled nonlinear rate equations are solved. To produce approximate analytical expressions for hemicelluloses, oligomers, and xylose concentrations for all the values of non-dimensional parameters and , the homotopy perturbation technique is applied. Our analytical results were compared to existing experimental data and found to be very similar. The dilute-acid pretreatment/hydrolysis of lignocellulosic biomass is studied using this mathematical model in the reactor.

Revalorization of sunflower stalk pith as feedstock for the coproduction of pectin and glucose using a two-step dilute acid pretreatment process

Background Sunflower stalk pith, residue from the processing of sunflower, is rich in pectin and cellulose, thereby acting as an economic raw material for the acquisition of these compounds. In order to increase the commercial value of sunflower processing industry, a two-step dilute sulfuric acid treatment process was conducted on spent sunflower stalk pith to obtain the value-added products, pectin and glucose. Results In this study, pectin was firstly extracted under mild acid condition to avoid pectin degradation, which was conducted at 90 °C with a pH of 2.0 for 2 h, and ~0.14 g/g of pectin could be recovered. Then the remaining solids after pectin extraction were subjected to the reinforced treatment process with 0.75% H2SO4 at 150 °C for 30 min to further improve enzymatic hydrolysis efficiency. Moreover, by combining a fed-batch enzymatic hydrolysis strategy, a solid loading content of 16% was successfully achieved and the glucose titer reached 103.1 g/L with a yield of 83.6%. Conclusion Finally, ~140 g pectin and 260 g glucose were produced from 1 kg of raw sunflower stalk pith using the integrated biorefinery process. This work puts forward a two-step dilute acid pretreatment combined with enzymatic hydrolysis method to produce pectin and glucose from sunflower spent waste.

Chemical Methods for Hydrolyzing Dairy Manure Fiber: A Concise Review

This paper reviews the chemical hydrolysis processes of dairy manure fiber to make its sugar accessible to microorganisms during anaerobic digestion and identifies obstacles and opportunities. Researchers, so far, investigated acid, alkali, sulfite, and advanced oxidation processes (such as hydrogen peroxide assisted by microwave/ultrasound irradiation, conventional boiling, and wet oxidation), or their combinations. Generally, dilute acid (3–10%) is less effective than concentrated acid (12.5–75%), which decrystallizes the cellulose. Excessive alkaline may produce difficult-to-degrade oxycellulose. Therefore, multi-step acid hydrolysis (without alkaline) is preferred. Such processes yielded 84% and 80% manure-to-glucose and -xylose conversion, respectively. Acid pretreatment increases lignin concentration in the treated manure and hinders subsequent enzymatic processes but is compatible with fungal cellulolytic enzymes which favor low pH. Manure high alkalinity affects dilute acid pretreatment and lowers glucose yield. Accordingly, the ratio of manure to the chemical agent and its initial concentration, reaction temperature and duration, and manure fineness need optimization because they affect the hydrolysis rate. Optimizing these factors or combining processes should balance removing hemicellulose and/or lignin and increasing cellulose concentrations while not hindering any subsequent process. The reviewed methods are neither economical nor integratable with the on-farm anaerobic digestion. Economic analysis and energy balance should be monolithic components of the research. More research is required to assess the effects of nitrogen content on these processes, optimize it, and determine if another pretreatment is necessary.

Mixed Acid Fermentation of Carbohydrate-Rich Dairy Manure Hydrolysate

Dairy manure (DM) is an abundant agricultural residue that is largely composed of lignocellulosic biomass. The aim of this study was to investigate if carbon derived from DM fibers can be recovered as medium-chain fatty acids (MCFAs), which are mixed culture fermentation products of economic interest. DM fibers were subjected to combinations of physical, enzymatic, chemical, and thermochemical pretreatments to evaluate the possibility of producing carbohydrate-rich hydrolysates suitable for microbial fermentation by mixed cultures. Among the pretreatments tested, decrystalization dilute acid pretreatment (DCDA) produced the highest concentrations of glucose and xylose, and was selected for further experiments. Bioreactors fed DCDA hydrolysate were operated. Acetic acid and butyric acid comprised the majority of end products during operation of the bioreactors. MCFAs were transiently produced at a maximum concentration of 0.17 mg CODMCFAs/mg CODTotal. Analyses of the microbial communities in the bioreactors suggest that lactic acid bacteria, Megasphaera, and Caproiciproducens were involved in MCFA and C4 production during DCDA hydrolysate metabolism.