L-lactic acid production from Lactobacillus casei by solid state fermentation using rice straw

In order to make full use of rice straw (RS) produced at large quantity in China and to reduce the production cost of L-lactic acid, attempts were made to utilize the hydrolysate of RS as sole carbon source and the lignocellulose as inert support for producing L-lactic acid using solid state fermentation (SSF). The pretreated rice straw was enzymatically hydro- lyzed by cellulase, and the hydrolyzate, containing reducing sugars supplemented with a minimum of (NH4)2SO4, MnSO4, and yeast extract, was used as moistening agent to impregnate 5g of RS, which was used as the inert support for SSF. Maximum L-lactic acid production of 3.467g per 5g of support was obtained at 37 oC, using Lactobacillus casei as inoculum, after 5 days of fermentation with optimized process parameters such as 72% moisture content, 4g per 5g support of reducing sugars, 2.5ml per 5g support of inoculum size, 3g per 5g support of CaCO3, and pH 6.5

Continuous Acetone–Butanol–Ethanol (ABE) Fermentation with in Situ Solvent Recovery by Silicalite-1 Filled PDMS/PAN Composite Membrane

The pervaporation (PV) performance of a thin-film silicalite-1 filled PDMS/PAN composite membrane was investigated in the continuous acetone–butanol–ethanol (ABE) production by a fermentation–PV coupled process. Results showed that continuous removal of ABE from the broth at three different dilution rates greatly increased both the solvent productivity and the glucose utilization rate, in comparison to the control batch fermentation. The high solvent productivity reduced the acid accumulation in the broths because most acids were reassimilated by cells for ABE production. Therefore, a higher total solvent yield of 0.37 g/g was obtained in the fermentation–PV coupled process, with a highly concentrated condensate containing 89.11–160.00 g/L ABE. During 268 h of the fermentation–PV coupled process, the PV membrane showed a high ABE separation factor of more than 30 and a total flux of 486–710 g/m2h. Membrane fouling was negligible for the three different dilution rates. The solution-diffusion model, especially the mass transfer equation, was proved to be applicable to this coupled process.<br/

Separation of monosaccharides from pretreatment inhibitors by nanofiltration in lignocellulosic hydrolysate: Fouling mitigation by activated carbon adsorption

Lignocellulose pretreatment results in production of hydrolysate consisting of sugars and inhibitors. Previous reports have shown the viability of nanofiltration (NF) of lignocellulosic hydrolysate for simultaneous sugar concentration and inhibitors removal. However, the complexity of real hydrolysate results in severe membrane fouling which greatly hinders the further application of NF in treating biomass hydrolysate. In this investigation, conditioning of real rice straw hydrolysate from dilute acid pretreatment was conducted by three methods (sedimentation, microfiltration (MF) and activated carbon (AC) adsorption) in order to reduce subsequent NF membrane fouling. Results showed that the turbidity, suspended substance (SS) and particle size of SS of the hydrolysate considerably decreased after these three conditioning methods. Only AC adsorption, however, exhibited best performance in terms of increasing the volume reduction ratio (VRR) and decreasing the membrane fouling during NF filtration of rice straw hydrolysate, demonstrating the effectiveness of AC adsorption for hydrolysate conditioning. Further experiments confirmed that removal of phenolics and pigments, the two dominating foulants during NF process, by AC adsorption were most likely responsible for its superior performance compared to sedimentation and MF

Recent insights into greywater treatment: a comprehensive review on characteristics, treatment technologies, and pollutant removal mechanisms

With the rapid socio-economic and industrial development, the problem of water shortage is becoming increasingly serious. Seeking alternative water sources to reduce the need for freshwater resources is an increasing concern. Household greywater production is high and accounts for about 50-80% of domestic wastewater. In recent years, the in situ treatment and reuse of greywater have received widespread attention. Treated greywater can be used for non-potable purposes such as toilet flushing and irrigation, which can greatly reduce the pressure of freshwater resource shortage. This paper reviews the sources and characteristics of greywater and analyzes its quantity and quality. In addition, this paper outlines and summarizes various greywater treatment technologies commonly used, including physical, biological, and chemical treatment technologies, as well as combination technologies. Understanding the mechanisms of contaminant removal is essential for effective greywater treatment. While discussing different treatment technologies, we focus on the removal mechanisms of pollutants from greywater, including organics, nutrients, surfactants, and emerging contaminants. Finally, future perspectives on greywater management and reuse are presented. Through a comprehensive review, we expect that this review will help the reader to better understand the characteristics of greywater and to more rationally select the appropriate treatment technology based on the removal mechanism of pollutants

Recent insights into greywater treatment: a comprehensive review on characteristics, treatment technologies, and pollutant removal mechanisms

With the rapid socio-economic and industrial development, the problem of water shortage is becoming increasingly serious. Seeking alternative water sources to reduce the need for freshwater resources is an increasing concern. Household greywater production is high and accounts for about 50-80% of domestic wastewater. In recent years, the in situ treatment and reuse of greywater have received widespread attention. Treated greywater can be used for non-potable purposes such as toilet flushing and irrigation, which can greatly reduce the pressure of freshwater resource shortage. This paper reviews the sources and characteristics of greywater and analyzes its quantity and quality. In addition, this paper outlines and summarizes various greywater treatment technologies commonly used, including physical, biological, and chemical treatment technologies, as well as combination technologies. Understanding the mechanisms of contaminant removal is essential for effective greywater treatment. While discussing different treatment technologies, we focus on the removal mechanisms of pollutants from greywater, including organics, nutrients, surfactants, and emerging contaminants. Finally, future perspectives on greywater management and reuse are presented. Through a comprehensive review, we expect that this review will help the reader to better understand the characteristics of greywater and to more rationally select the appropriate treatment technology based on the removal mechanism of pollutants

Bioresour. Technol.

Pretreatment of lignocellulosic material produces a wide variety of inhibitory compounds, which strongly inhibit the following enzymatic hydrolysis of cellulosic biomass. Vanillin is a kind of phenolics derived from degradation of lignin. The effect of vanillin on cellulase activity for the hydrolysis of cellulose was investigated in detail. The results clearly showed that vanillin can reversibly and non-competitively inhibit the cellulase activity at appropriate concentrations and the value of IC50 was estimated to be 30 g/L. The inhibition kinetics of cellulase by vanillin was studied using HCH-1 model and inhibition constants were determined. Moreover, investigation of three compounds with similar structure of vanillin on cellulase activity demonstrated that aldehyde group and phenolic hydroxyl groups of vanillin had inhibitory effect on cellulase. These results provide valuable and detailed information for understanding the inhibition of lignin derived phenolics on cellulase. (C) 2014 Elsevier Ltd. All rights reserved.Pretreatment of lignocellulosic material produces a wide variety of inhibitory compounds, which strongly inhibit the following enzymatic hydrolysis of cellulosic biomass. Vanillin is a kind of phenolics derived from degradation of lignin. The effect of vanillin on cellulase activity for the hydrolysis of cellulose was investigated in detail. The results clearly showed that vanillin can reversibly and non-competitively inhibit the cellulase activity at appropriate concentrations and the value of IC50 was estimated to be 30 g/L. The inhibition kinetics of cellulase by vanillin was studied using HCH-1 model and inhibition constants were determined. Moreover, investigation of three compounds with similar structure of vanillin on cellulase activity demonstrated that aldehyde group and phenolic hydroxyl groups of vanillin had inhibitory effect on cellulase. These results provide valuable and detailed information for understanding the inhibition of lignin derived phenolics on cellulase. (C) 2014 Elsevier Ltd. All rights reserved

Immobilization of cellulase on a core-shell structured metal-organic framework composites: Better inhibitors tolerance and easier recycling

For the first time, cellulase was successfully immobilized on a magnetic core-shell metal-organic framework (MOF) material, UIO-66-NH2. The as-prepared immobilized cellulase demonstrated a high protein loading efficiency of 126.2 g/g support and a high enzyme activity recovery of 78.4%. Cellulase immobilized on magnetic UIO-66-NH2 exhibited a superior performance in terms of pH stability, thermal stability and catalytic efficiency compared to its free form. Notably, immobilized cellulase could be recycled for up to 5 consecutive runs. Furthermore, compared to free cellulase, immobilized cellulase showed better tolerance to formic acid and vanillin, two typical inhibitors found in lignocellulosic prehydrolysates. In the presence of 5 g/L of formic acid and vanillin, immobilized cellulase demonstrated 16.8% and 21.5% higher activity than free enzyme, respectively, and its improvement in hydrolysis yield was 18.7% and 19.6% respectively. This is firstly confirmed that immobilization can alleviate the inhibitory effects of certain pretreatment inhibitors on cellulase.</p

Pretreatment of wheat straw by nonionic surfactant-assisted dilute acid for enhancing enzymatic hydrolysis and ethanol production

Pretreating wheat straw (WS) with combined use of varied sulfuric acid concentration (0-3%, w/v) and Tween 20 concentration (0-1%) was investigated in an attempt to enhance the hydrolysis and fermentability of pretreated WS. Enzymatic hydrolysis yield of glucan and xylan and ethanol production by simultaneous saccharification and fermentation (SSF) of water-insoluble solids (WIS) were significantly affected by the amount of Tween 20 added during acid pretreatment. Any further addition of Tween 20 in either hydrolysis stage or fermentation stage only led to small increase in glucan conversion and ethanol production. Determination of adsorption of cellulases during hydrolysis showed that Tween 20-assisted acid treated straw solution contained more free cellulases than individual acid treated straw solution, indicating that modification of lignin surface by Tween 20 added during pretreatment likely occurred. In addition, the effects of pretreatment conditions on overall recovery of glucose and xylose after pretreatment and enzymatic hydrolysis were also investigated. (C) 2010 Elsevier Ltd. All rights reserved

Pretreatment of corn stover by acidic and basic choline chloride solutions for enzymatic hydrolysis

As a cheap, biodegradable, and nontoxic chemical, choline chloride (ChCl) is widely used in animal feed. In this study, acid and alkali catalyzed ChCl pretreatments of corn stover (CS) were investigated. Compared with single aqueous ChCl pretreatment, H2SO4 acidified aqueous ChCl pretreatment was more effective in removing lignin (69.5%) and xylan (84.9%). NaOH alkalified aqueous ChCl pretreatment demonstrated better performance of delignification (76.8%) but weaker capability of removing xylan (46.2%) than acidified aqueous ChCl pretreatment. Following enzymatic digestibility of pretreated CS, glucose yield from acidified ChCl pretreatment was 72.1%, significantly lower than that of alkalified ChCl pretreatment (89.4%). However, the highest glucose yield of 98.6% resulted from solitary alkali pretreatment. Correlation studies between change in physico-chemical properties of pretreated solids and corresponding enzymatic digestibility indicated high delignification and bigger cellulose crystallite size were mainly responsible for high enzymatic hydrolysis efficiency. Additionally, the properties of extracted lignin from single and combined pretreatments with ChCl and alkali or acid were analyzed. Acidified ChCl pretreatment increased, whereas alkaline ChCl pretreatment decreased molecular weight and phenolic hydroxyl groups of separated lignin in comparison to individual acid and alkali pretreatment. These findings would provide useful information in understanding biomass pretreatments with aqueous ChCl

Sep. Purif. Technol.

Simultaneous extraction of oil and soy isoflavones from soy sauce residue (SSR) was investigated by means of the two-phase solvent extraction intensified by ultrasonication. A single factor test was first carried out to study the effects of ultrasonic time, ethanol concentration, ratio of ethanol/water phase to raw material, ratio of hexane phase to raw material, and ultrasonic power on the extraction rates of oil and isoflavones, then response surface methodology was applied to further optimize and simulate four key factors. The results showed that the extraction rates of oil and isoflavones of 92.07% and 92.53%, respectively, could be obtained when ethanol concentration was 74.88%, ratio of ethanol/water phase to raw material 15:1, ratio of hexane phase to raw material 8.64:1, extraction time 20 min, and ultrasonic power 160 W. The predictive rates were well matched with the experimental ones. The quality analysis of oil and soy isoflavones from SSR showed that the extracted oil with high acid value could be a potential raw material for biodiesel production instead of cooking. The extracted soy isoflavones existed mainly in aglycones form, which might afford higher bioactivity than that from the other soybean products. (C) 2014 Elsevier B.V. All rights reserved.Simultaneous extraction of oil and soy isoflavones from soy sauce residue (SSR) was investigated by means of the two-phase solvent extraction intensified by ultrasonication. A single factor test was first carried out to study the effects of ultrasonic time, ethanol concentration, ratio of ethanol/water phase to raw material, ratio of hexane phase to raw material, and ultrasonic power on the extraction rates of oil and isoflavones, then response surface methodology was applied to further optimize and simulate four key factors. The results showed that the extraction rates of oil and isoflavones of 92.07% and 92.53%, respectively, could be obtained when ethanol concentration was 74.88%, ratio of ethanol/water phase to raw material 15:1, ratio of hexane phase to raw material 8.64:1, extraction time 20 min, and ultrasonic power 160 W. The predictive rates were well matched with the experimental ones. The quality analysis of oil and soy isoflavones from SSR showed that the extracted oil with high acid value could be a potential raw material for biodiesel production instead of cooking. The extracted soy isoflavones existed mainly in aglycones form, which might afford higher bioactivity than that from the other soybean products. (C) 2014 Elsevier B.V. All rights reserved