Statistical optimization,partial purification,and characterization of coffee pulp β-glucosidase and its application in ethanol production

Extracellular β-glucosidase was produced using coffee pulp as a sole carbon source by Penicillium verrucosum by solid state fermentation and 897.36±59 U/g enzyme activity was obtained. Increase in 2.21-fold of enzyme activity on optimizing the bioprocess parameters by response surface methodology based on central composite rotatable design is illustrated. Maximum production level of 1,991.17 U/g was obtained with optimum values of pH 4.2, moisture 66.8%, and fermentation duration of 56 h. The enzyme was partially purified and the enzyme activity was optimum at 50°C temperature and at pH 6. The metal ions such as Mg²⁺, Zn²⁺, Ca²⁺, K⁺, detergents, and chelator such as EDTA were effective and further increased the β-glucosidase activity. On application of β-glucosidase for simultaneous saccharifiation and fermentation, 3.3% ethanol was obtained. Thus, this study provides insight on exploitation of P. verrucosum for synthesis of of β-glucosidase using coffee pulp which is available abundantly in coffee processing industries.

     

Fenton oxidation and adsorption pretreatment for superior biogas recovery from biomethanated spent wash

Abstract

A key task in alcohol distilleries is the effective treatment of biomethanated spent wash after biogas recovery. This colored washwater exhibits low biodegradability index (BI?<?0.2), high chemical oxygen demand (30,000?<?COD?<?40,000?mg/L), and recalcitrance to aerobic treatment. In this work, pretreatment of biomethanated distillery wastewater by Fenton oxidation was proposed for improved biogas recovery. The effects of temperature, solution pH, and H₂O₂ dosage on the efficacy of the oxidation process were studied. Using ferrous sulfate catalyst (36?mg/L) for diluted wastewater (BOD₅?=?81; COD?=?400?mg/L), 54% reduction in COD was achieved within 1?h in acidic medium (pH?=?3) at ambient temperature (T?=?30?°C). Post-oxidation, the BI value improved (0.33). After subsequent adsorption over activated carbon (loading 5%) for 1?h, COD reduction (70%), and BI value (0.43) improved further. Upon anaerobic treatment with 1% acclimatized biomass, 1?Nm³ of biogas (47% CH₄) was additionally formed per m³ of treated wastewater; without pretreatment, this value was 0.9?Nm³ (just 11% CH₄). Lastly, aerobic treatment was performed and the results were encouraging: BI?=?0.51 and COD reduction?=?94%. Many oxidation products were identified and first-order kinetic plots were made to describe COD conversion kinetics. In this way, useful insight on a plausible technique for valorization of biomethanated washwater was provided.