Abdul Sattar Qureshi

Dry biorefining maximizes the potentials of simultaneous saccharification and co-fermentation for cellulosic ethanol production†

Despite the well‐recognized merits of simultaneous saccharification and co‐fermentation (SSCF) on relieving sugar product inhibition on cellulase activity, a practical concomitance difficulty of xylose with inhibitors in the pretreated lignocellulose feedstock prohibits the essential application of SSCF for cellulosic ethanol fermentation. To maximize the SSCF potentials for cellulosic ethanol production, a dry biorefining approach was proposed starting from dry acid pretreatment, disk milling, and biodetoxification of lignocellulose feedstock. The successful SSCF of the inhibitor free and xylose conserved lignocellulose feedstock after dry biorefining reached a record high ethanol titer at moderate cellulase usage and minimum wastewater generation. For wheat straw, 101.4 g/L of ethanol (equivalent to 12.8% in volumetric percentage) was produced with the overall yield of 74.8% from cellulose and xylose, in which the xylose conversion was 73.9%, at the moderate cellulase usage of 15 mg protein per gram cellulose. For corn stover, 85.1 g/L of ethanol (equivalent to 10.8% in volumetric percentage) is produced with the overall conversion of 84.7% from cellulose and xylose, in which the xylose conversion was 87.7%, at the minimum cellulase usage of 10 mg protein per gram cellulose. Most significantly, the SSCF operation achieved the high conversion efficiency by generating the minimum amount of wastewater. Both the fermentation efficiency and the wastewater generation in the current dry biorefining for cellulosic ethanol production are very close to that of corn ethanol production, indicating that the technical gap between cellulosic ethanol and corn ethanol has been gradually filled by the advancing biorefining technology.

Antibacterial activity of graphene supported FeAg bimetallic nanocomposites.

We report the simple one pot synthesis of iron-silver (FeAg) bimetallic nanoparticles with different compositions on graphene support. The nanoparticles are well dispersed on the graphene sheet as revealed by the TEM, XRD, and Raman spectra. The antibacterial activity of graphene-FeAg nanocomposite (NC) towards Bacillus subtilis, Escherichia coli, and Staphylococcus aureus was investigated by colony counting method. Graphene-FeAg NC demonstrates excellent antibacterial activity as compared to FeAg bimetallic without graphene. To understand the antibacterial mechanism of the NC, oxidative stress caused by reactive oxygen species (ROS) and the glutathione (GSH) oxidation were investigated in the system. It has been observed that ROS production and GSH oxidation are concentration dependent while the increase in silver content up to 50% generally enhances the ROS production while ROS decreases on further increase in silver content. Graphene loaded FeAg NC demonstrates higher GSH oxidation capacity than bare FeAg bimetallic nanocomposite. The mechanism study suggests that the antibacterial activity is probably due to membrane and oxidative stress produced by the nanocomposites. The possible antibacterial pathway mainly includes the non-ROS oxidative stress (GSH oxidation) while ROS play minor role.

Production and Partial Characterization of α-Amylase Enzyme from Bacillus sp. BCC 01-50 and Potential Applications

Amylase is an industrially important enzyme and applied in many industrial processes such as saccharification of starchy materials, food, pharmaceutical, detergent, and textile industries. This research work deals with the optimization of fermentation conditions for α-amylase production from thermophilic bacterial strain Bacillus sp. BCC 01-50 and characterization of crude amylase. The time profile of bacterial growth and amylase production was investigated in synthetic medium and maximum enzyme titer was observed after 60 h. In addition, effects of different carbon sources were tested as a substrate for amylase production and molasses was found to be the best. Various organic and inorganic compounds, potassium nitrate, ammonium chloride, sodium nitrate, urea, yeast extract, tryptone, beef extract, and peptone, were used and beef extract was found to be the best among the nitrogen sources used. Temperature, pH, agitation speed, and size of inoculum were also optimized. Highest enzyme activity was obtained when the strain was cultured in molasses medium for 60 h in shaking incubator (150 rpm) at 50°C and pH 8. Crude amylase showed maximal activity at pH 9 and 65°C. Enzyme remained stable in alkaline pH range 9-10 and 60–70°C. Crude amylase showed great potential for its application in detergent industry and saccharification of starchy materials.

Lower pressure heating steam is practical for the distributed dry dilute sulfuric acid pretreatment

Most studies paid more attention to the pretreatment temperature and the resulted pretreatment efficiency, while ignored the heating media and their scalability to an industry scale. This study aimed to use a relative low pressure heating steam easily provided by steam boiler to meet the requirement of distributed dry dilute acid pretreatment. The results showed that the physical properties of the pretreated corn stover were maintained stable using the steam pressure varying from 1.5, 1.7, 1.9 to 2.1MPa. Enzymatic hydrolysis and high solids loading simultaneous saccharification and fermentation (SSF) results were also satisfying. CFD simulation indicated that the high injection velocity of the low pressure steam resulted in a high steam holdup and made the mixing time of steam and solid corn stover during pretreatment much shorter in comparison with the higher pressure steam. This study provides a design basis for the boiler requirement in distributed pretreatment concept.

Production, Purification and Partial Characterization of Organo-Solvent Tolerant Protease from Newly Isolated Bacillus sp. BBXS-2

Proteolytic enzymes are applied in various industries such as detergent, leather, food, textile, cosmetics, pharmaceutical, and synthetic biotechnology. To meet commercial needs, microbial strains of high value in terms of cost-effective production have been focused. In this study, thermophilic strain, Bacillus sp. BBXS-2 was activated on simple growth medium and then transferred to Luria Bertani (LB) medium. Maximum protease concentration of 6723 U/mL under optimized fermentation conditions (molasses, corn steep liquor, pH 9.0, and 45°C). The results showed, there was no difference observed in bacterial growth and protease titer while replacing yeast extract with corn steep liquor so, in this way, about 90% cost of nitrogen source can be saved. The extracellular enzyme was purified to homogeneity from cell-free supernatant by ammonium sulphate precipitation followed by dialysis and ion exchange chromatography, recovery yield reduced from 100 to 22% and purification fold increased from 1 to 9.82. The enzyme was active in broad pH and temperature range 8-12 pH and 30-60°C, with maximum activity at pH 10.0 and 60°C, respectively. Protease retained more than 90% activity after incubation at 40°C for 2 weeks in the presence of (40% v/v) organic solvents including ethanol, methanol, and isopropanol. Overall, research suggests that this strain is a more promising candidate and possess practical ability to use in industries.

Improved transesterification of waste cooking oil into biodiesel using calcined goat bone as a catalyst

ABSTRACT In this study, potassium hydroxide-treated animal bones were employed as a solid heterogeneous catalyst in transesterification of waste cooking oil. This catalyst was characterized by the Fourier-transform infrared spectroscopy (FTIR), and it displayed high-catalytic activity for biodiesel production. Optimum conditions for biodiesel production were catalyst loading 6.0% (w/w) of oil, methanol/oil molar ratio 9:1, calcination temperature 800°C, reaction temperature 65°C, and reaction time of 5 h, which gave maximum biodiesel yield of 84%. Reusability of the catalyst was also confirmed by repeated use of the same catalyst three times without losing much of its activity. Hence, calcined goat bones were found to be a potentially applicable catalyst for biodiesel production at industrial scale.