BACKGROUND The deactivation of cellulases by phenolics is considered to be the main bottleneck in the saccharification of agricultural by‐products for efficient bioethanol production on a large scale. The removal of these phenolic inhibitors, produced as a result of pretreatment, is essential for an efficient saccharification process. One such process is overliming that has been mostly studied for hydrolysates of agricultural by‐products. In the present study however, solid biomass was used whereby the detection of phenolic compounds and their effect on saccharification was studied. RESULTS The pretreated wheat straw showed 19% saccharification and total phenolic content (TPC) of 188 mg gallic acid equivalent g‐1 biomass dry weight. Detoxification of pretreated wheat straw applying different alkalis, i.e. NaOH, NH4OH and Ca(OH)2 was conducted. Overliming using Ca(OH)2 solution of pH 12, for 2 h at 80°C showed significant removal of 60% of phenolic compounds, which in turn enhanced the saccharification by 2.4‐fold. Scanning electron microscopy of pretreated and overlimed substrates also showed considerable change in structure, making it more accessible for enzymatic hydrolysis. CONCLUSION The elimination of phenolic compounds due to overliming has facilitated increased saccharification that in turn will help in substrate efficient biofuel production. © 2018 Society of Chemical Industry

Depleting supplies of fossil fuel, regular price hikes of gasoline and environmental deterioration have necessitated the search for economic and eco-benign alternatives of gasoline like lignocellulosic biomass. However, pre-treatment of such biomass results in development of some phenolic compounds which later hinder the depolymerisation of biomass by cellulases and seriously affect the cost effectiveness of the process. Dephenolification of biomass hydrolysate is well cited in literature. However, elimination of phenolic compounds from pretreated solid biomass is not well studied. The present study was aimed to optimize dephenoliphication of wheat straw using various alkalis i.e., Ca(OH)2 and NH3; acids i.e., H2O2, H2SO4, and H3PO4; combinations of NH3+ H3PO4 and H3PO4+ H2O2 at pilot scale to increase enzymatic saccharification yield. Among all the pretreatment strategies used, maximum reduction in phenolic content was observed as 66 mg Gallic Acid Equivalent/gram Dry Weight (GAE/g DW), compared to control having 210 mg GAE/g DW using 5% (v/v) combination of NH3+H3PO4. Upon subsequent saccharification of dephenoliphied substrate, the hydrolysis yield was recorded as 46.88%. Optimized conditions such as using 1%+5% concentration of NH3+ H3PO4, for 30 min at 110°C temperature reduced total phenolic content (TPC) to 48 mg GAE/g DW. This reduction in phenolic content helped cellulases to act more proficiently on the substrate and saccharification yield of 55.06% was obtained. The findings will result in less utilization of cellulases to get increased yield of saccharides by hydrolyzing wheat straw, thus, making the process economical. Furthermore, pilot scale investigations of current study will help in upgrading the novel process to industrial scale.

Modelado de la biodegradación en biorreactores de lodos de hidrocarburos totales del petróleo intemperizados en suelos y sedimentos (Biodegradation modeling of sludge bioreactors of total petroleum hydrocarbons weathering in soil and sediments)

Modelado de la biodegradación en biorreactores de lodos de hidrocarburos totales del petróleo intemperizados en suelos y sedimentos (Biodegradation modeling of sludge bioreactors of total petroleum hydrocarbons weathering in soil and sediments)

Background: Fruit juice clarification is a challenging aspect of beverage industry which needs to be addressed for economical and hygienic production of fruit juices. Objective: Current study is focused on the complete purification, characterization and thermodynamic analysis of an efficient mannanase enzyme to analyze its applicability in biological clarification fruit juice. Methods: Mannanase production using Aspergillus awamori IIB037 in a 25 L stirred fermenter at pre optimized reaction conditions was carried out. Enzyme purification was carried out via series of steps. Characterization of enzyme along with kinetics and thermodynamic studies was conducted. Purified and characterized enzyme was assessed for its applicability in fruit juice clarification through clarification experiments on fresh apple juice. Results: Purification fold of 3.98 was obtained along with 86.80% purification yield of mannanase with specific activity of 158.16 U/mg. The molecular size of purified enzyme was determined as 66 kDa. The enzyme depicted 56% residual activity at 60°C after 8 hrs. Thermodynamic studies of an enzyme revealed enthalpy of activation (ΔH) and activation energy (Ea) as 30.53KJ/mol, 27.76KJ/mol, respectively. The enzyme activity increased in the presence of ß-mercaptoethanol surprisingly. On the other hand, methyl alcohol, ethanol, Hg2+ and Cu2+ inhibited enzyme activity. The enzyme showed Km and Vmax values of 11.07 mM and 19.08 µM min-1 for Locust Bean Gum (LBG) under optimal conditions. Juice treated with mannanase showed decrease in absorbance and increase in reducing sugar content. Conclusion: The current study demonstrated that mannanase from Aspergillus awamori in its purified form has significant characteristics to be employed industrially for juice clarification.

No abstract