Optimization of fermentation condition for co-production of ethanol and 2,3-butanediol (2,3-BD) from hemicellolosic hydrolysates by Klebsiella oxytoca XF7

Microbial production of ethanol and 2,3-butanediol (2,3-BD) from agro-residues has been attracting interest because of their applications in various industries, including generation of biofuel molecules. In the present investigation, the hemicellulosic fraction of corncob was hydrolyzed by indigenous holocellulase from novel psychrotolerant Aspergillus niger SH3 resulting in high xylose release (34.61?g?L^?1), followed by the bioconversion of xylose to ethanol and 2,3-BD. Taguchi design was adopted to optimize the process which resulted in 5.25- and 3.31-fold increase in 2,3-BD (12.18?±?0.53?g?L^?1) and ethanol (4.08?±?0.03?g?L^?1), as compared with un-optimized condition. For the first time, co-production of ethanol and 2,3-BD from the corncob hemicellulosic hydrolysate was performed using a newly isolated Klebsiella oxytoca XF7 strain, under the optimized fermentation conditions. These results suggest that K. oxytoca XF7 is a promising candidate for co-production of ethanol and 2,3-BD, with high xylose conversion efficiency (96.65%), facilitating the economical production of biofuel molecules.     

Roles of soluble and insoluble aggregates induced by soy protein processing in the gelation of myofibrillar protein

The role of soluble and insoluble aggregates induced by soy protein isolate (SPI) processing in the gelling properties of myofibrillar protein (MP) was studied. Incorporating soluble SPI aggregate could greatly improve (P < 0.05) the elastic modulus (G’) and water‐holding capacity (WHC) of MP gel, but had no notable effect on MP gel strength. In contrast, incorporating the insoluble SPI aggregate significantly enhanced the G’, strength and WHC of MP gel, although the improvement in WHC was smaller than that produced by the soluble aggregate. The results of environmental scanning electron microscopy showed that the soluble SPI aggregate induced a less randomly composite gel structure, which may explain its notable enhancement of WHC. However, the insoluble SPI aggregate appeared to be granules embedded in the continuous MP gel matrix, which may be related to the reinforcement of gel strength. Hence, the results of this study suggest further means of processing commercial SPI for use in meat products.     

Thermal behavior of poly(ethylene‐co‐propylene) containing carbon nanofibers

The effect of carbon nanofiber on the thermal behavior of poly(ethylene‐co‐propylene) (PEP) as revealed by differential scanning calorimetry and thermogravimetric analysis is reported. Analysis showed faster crystallization of PEP at higher temperature upon cooling with the increase of carbon nanofiber (CNF) content. The crystallization behavior changed to a single narrow crystallization peak as compared with the broad double crystallization peak of the neat polymer. This demonstrates the nucleation ability of CNF to induce crystals with more uniform distribution. The modified‐Avrami approach was used to study the crystallization behavior. We found that the crystallization rate constant increased with addition of CNFs. The dimensionality of crystal growth was found not to depend significantly on the content of CNF. Thermal degradation in air was monitored using thermogravimetric analysis and observed that the incorporation of nanofiber greater than 2.4 vol% improves thermal stability of PEP. All these results indicate that CNFs can significantly help polymer processing and increase thermal stability of polymers. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

High‐pressure microfluidisation pretreatment disaggregate peanut protein isolates to prepare antihypertensive peptide fractions

High‐pressure microfluidisation (HPM) pretreatment was applied to increase in vitro antihypertensive activity of peanut peptide fractions (PPF). The morphology of protein in aqueous dispersion revealed that peanut protein isolate (PPI) disaggregated at relatively low pressure (≤120 MPa) and re‐aggregated at relatively high pressures (150–210 MPa). The treated pressure of 120 MPa could lead to the most disaggregation of PPI. Small peptides contents, trichloroacetic acid‐nitrogen soluble index (TCA‐NSI) and degree of hydrolysis (DH) of peanut protein hydrolysates (PPH) all reached the highest at 120 MPa. Consequently, it possessed the highest angiotensin converting enzyme (ACE) and renin inhibitory activity. The highest surface hydrophobicity occurred at 120 MPa pretreatment samples. Thirty‐nine oligopeptides at 120 MPa pretreatment were identified by ultra‐performance liquid chromatography‐quadrupole time‐of‐flight (UPLC‐Q‐TOF) mass spectrometer combined with Progenesis QI for Proteomics software compared with 29 and 35 at control and 210 MPa, respectively. This meant that disaggregation of PPI at 120 MPa resulted in the release of new hydrophobic peptide.     

Drying of Burdock Root Cubes Using a Microwave-Assisted Pulsed Spouted Bed Dryer and Quality Evaluation of the Dried Cubes

Burdock cube samples were dried using hot air and microwave pulsed spouted bed drying (MPSBD). Hot air drying was carried out at three temperatures (70, 80, and 90°C). MPSBD was carried out at three microwave power levels (1.0, 2.0, and 3.0 W/g). The results showed that MPSBD samples dried at 2.0 W/g for 30 min and at 1.0 W/g for 40 min had desirable color, flavor, and textural attributes. Gas chromatography–mass spectrometry results showed that the samples dried using MPSBD were richer in flavor compounds, especially in esters, compared to the hot air–dried samples.     

Experimental studies and kinetics of single drop drying and their relevance in drying of sugar‐rich foods: A review

Levitation and free‐flight techniques applied to investigate the drying kinetics and morphology of single drops containing dissolved solids and suspensions are reviewed. A review of works related to receding interface model proposed to quantify the drying kinetics of single drops along with techniques to measure the kinetic parameters such as moisture diffusivity, thermal conductivity and specific heat capacity is presented. Problems associated with spray drying of sugar‐rich compounds are briefly discussed and possible links of stickiness and flavor retention with glass transition temperature (T_g), temperature history, drying rate and morphological changes including skin formation, as monitored through single drop experiments, are explored.