Modeling and simulation of a sawdust mixture-based integrated biorefinery plant producing bioethanol.

The design, modeling and simulation of an integrated biorefinery plant assumed to convert different forestry assortments such as sawdust or shavings (sawmill waste) into bioethanol from cellulose and hemicellulose as the main product, and lignin as the most valuable co-product, was carried out. The proposed lignocellulosic ethanol biorefinery plant was simulated with ProSimPlus. The model was based on experimental results and includes an Organosolv pretreatment, enzymatic hydrolysis, fermentation and distillation to obtain bioethanol. The investigated plant size processed 70,088 tons of biomass/year, with a production capacity of 11,650 tons ethanol/year. Ethanol productivity reached 351 L/ton of dry feedstock. Considering water consumption, approximately 4.8 L of water were needed to produce a liter of ethanol. Finally, the energy targeting through conventional pinch analysis lead to 16.4 MW and 16.07 MW of hot and cold utility energy demand for the entire process respectively with the cogeneration of electricity.

Hydrolysis and fermentation steps of a pretreated sawmill mixed feedstock for bioethanol production in a wood biorefinery.

The aim of this work was to demonstrate the feasibility of second-generation bioethanol production using for the first time a sawmill mixed feedstock comprising four softwood species, representative of biomass resource in Auvergne-Rhône-Alpes region (France). The feedstock was subjected to a microwave-assisted water/ethanol Organosolv pretreatment. The investigation focused on enzymatic hydrolysis of this pretreated sawmill feedstock (PSF) using Cellic® Ctec2 as the enzyme, followed by fermentation of the resulting sugar solution using Saccharomyces cerevisiae strain. The cellulose-rich PSF with 71% w/w cellulose content presented high saccharification yields (up to 80%), which made it perfect for subsequent fermentation; this yield was predicted vs. time up to 5.2% w/v PSF loading using a mathematical model fitted only on data at 1.5%. Finally, high PSF loading (7.5%) and scaleup were shown to impair the saccharification yield, but alcoholic fermentation could still be carried out up to 80% of the theoretical glucose-to-ethanol conversion yield.

Optimization of lactic acid production using immobilized Lactobacillus Rhamnosus and carob pod waste from the Lebanese food industry.

The valorization of a solid carob waste from the Lebanese industry was investigated by optimizing the production of lactic acid using immobilized Lactobacillus rhamnosus in alginate beads and response surface methodology. The results showed that pH and alginate concentration had a significant effect on the production of lactic acid. The fermentation of non-enriched carob waste juice needed an additional nitrogen source to improve lactic acid production and yield. From extracts with 65 g/L sugars, the optimum conditions were found to be 2% for the concentration of alginate, 4% bacteria cells entrapped in beads, 80 rpm agitation speed and pH 6.4. Lactic acid concentration obtained under these conditions was 22 g/L with a yield of 76.9 g/g consumed sugar and a productivity of 1.22 g/L/h. The use of invertase pretreatment increased lactic acid concentration from 22 to 40 g/L, but reduced yield at 66.6%. Finally, cells immobilized in alginate beads could be used for at least five successive cycles.

Microwave-assisted Organosolv pretreatment of a sawmill mixed feedstock for bioethanol production in a wood biorefinery.

A mixture of sawmill feedstocks comprising four softwood species (fir, spruce, Scots pine, and Douglas fir) was subjected to a microwave-assisted Organosolv pretreatment. The influence of H2SO4 as a catalyst, ethanol-water ratio as the solvent, and temperature on wood fractionation, cellulose yield and purity, lignin recovery, and inhibitor formation were investigated. Minute addition of H2SO4 (0.25% w/w) was found to enhance lignin extraction and hemicellulose hydrolysis, thus providing cellulose yield and purity above 68% ±â€¯2% and 61% ±â€¯3%, respectively. The increase in H2SO4 up to 1% and temperature up to 190 °C, impaired cellulose yields a result of intense hydrolysis, thus degrading cellulose and hemicellulose. Conversely, the increase in ethanol-water ratio enhanced delignification without cellulose degradation. Similarly, inhibitor formation increased with pretreatment severity (H2SO4 content and temperature), but was mitigated by higher ethanol-water ratio. Finally, under best conditions (60:40 ethanol-water, 175 °C, 0.25% H2SO4), cellulose yield and purity reached 82% ±â€¯3% and 71% ±â€¯3%, respectively.

High-frequency, high-intensity electromagnetic field effects on Saccharomyces cerevisiae conversion yields and growth rates in a reverberant environment.

Studies of the effects of electromagnetic waves on Saccharomyces cerevisiae emphasize the need to develop instrumented experimental systems ensuring a characterization of the exposition level to enable unambiguous assessment of their potential effects on living organisms. A bioreactor constituted with two separate compartments has been designed. The main element (75% of total volume) supporting all measurement and control systems (temperature, pH, agitation, and aeration) is placed outside the exposure room whereas the secondary element is exposed to irradiation. Measurements of the medium dielectric properties allow the determination of the electromagnetic field at any point inside the irradiated part of the reactor and are consistent with numerical simulations. In these conditions, the growth rate of Saccharomyces cerevisiae and the ethanol yield in aerobic conditions are not significantly modified when submitted to an electromagnetic field of 900 and 2400 MHz with an average exposition of 6.11 V.m-1 and 3.44 V.m-1 respectively.

Valorization of carob waste: Definition of a second-generation bioethanol production process.

The aim of this work was to develop a strategy for second-generation ethanol production from carob solid waste issued from Lebanese food industry. The pros and cons of submerged (SF) and solid-state fermentations (SSF) using S. cerevisiae on ethanol yield and productivity were compared, including the respective roles of upstream and downstream processes, such as the size reduction, or sugar and ethanol recovery processes. The design of experiments methodology was applied. Experimental results demonstrated that SSF applied to cut carob waste from carob syrup preparation was simpler to operate and more cost-effective, maintained yield and productivity (0.458g ethanol/g consumed sugar and 4.3g/(kg waste)/h) in comparison to SF (0.450g ethanol/g consumed sugar and 5.7g/(kg waste)/h), and was able to achieve ethanol production up to 155g/(kg waste) at low water demand, while SF reached only 78g/(kg waste) due to the limitations of the sugar extraction pretreatment.

Application of a data reconciliation method to the stoichiometric analysis of Fibrobacter succinogenes growth.

Fibrobacter succinogenes S85, a strictly anaerobic Gram-negative bacterium, was grown in continuous culture in a bioreactor at different dilution rates (0.02 to 0.092 h(-1)) on a fully synthetic culture medium with glucose as carbon source. Glucose and ammonium sulfate consumption, as well as biomass, succinate, acetate, formate, and carbohydrate production were regularly measured. The relevant biomass elemental compositions were established for each dilution rate. Robustness of the experimental information was checked by C and N mass balances estimation, which were satisfactory. A detailed overall stoichiometry analysis of the process, including all substrates and products of the culture, was proposed. Online and off-line parameters measured during the culture brought a large number of data which were weighted by their respective variance associated to the measured value. The material balance resulted in an overdetermined linear system of equations made of weighted relationships including experimental data, elemental balances (C, H, O, N, S, Na), and an additional constraint. The mass balances involved in stoichiometric equations were solved using data reconciliation and linear algebra methods to take into account error measurements. This methodology allowed to establish the overall stoichiometric equation for each dilution rate studied.