Utilization of lignocellulosic waste for ethanol production: Enzymatic digestibility and fermentation of pretreated shea tree sawdust

Enzymatic hydrolysis and fermentation methods were evaluated on alkaline peroxide pretreated shea tree sawdust conversion to ethanol. Optimum pretreatment conditions of 120 oC reaction temperature, 30 min reaction time, and 20 mL L−1 of water hydrogen peroxide concentration (1%(v/v)H2O2) solubilized 679 g kg−1 of hemicellulose and 172 g kg−1 of lignin. 617 g kg−1 cellulose was retained in the solid fraction. The maximum yield of reducing sugar with optimized enzyme loadings by two enzyme preparations (cellulase and β-glucosidase) was 165 g kg−1 of dry biomass. The ethanol yield was 7.35 g L−1 after 72 h incubation period under the following conditions: 2% cellulose loading, enzyme concentration was 25 FPU (g cellulose)−1 loading, yeast inoculums was 10% (v/v), 32 oC, and pH 4.8. The pretreatments gave information about the hindrances caused by lignin presence in lignocellulosic materials and that hemicelluloses are better hydrolyzed than lignin, thereby enhancing enzymatic digestibility of the sawdust materia

Hydrogen peroxide and lime based oxidative pretreatment of wood waste to enhance enzymatic hydrolysis for a biorefinery: Process parameters optimization using response surface methodology

Response surface methodology (RSM) was adopted for the optimization of process variables in the alkaline peroxide oxidation (APO) pretreatment of Vitellaria paradoxa sawdust based on central composite design (CCD) experiments. A 23 five level CCD with central and axial points was used to develop a statistical model for the optimization of process variables. Maximum response for the pretreatment was obtained when applying the optimum values for temperature (150 �C), time (45 min), and 1% (v/v) H2O2. At the optimum conditions, up to 70% of the initial hemicellulose was removed in treatments, which also caused some delignification (up to 11% of the initial lignin was removed), whereas cellulose was almost quantitatively retained in the solid phase. Alkaline peroxide assisted wet air oxidation (APAWAO) pretreatment at the optimum conditions resulted in enrichment up to 60% cellulose content along with solubilization of 80% hemicellulose and 17% of lignin initially present in the raw sawdust. Reducing sugars yield after 72 h enzymatic hydrolysis of pretreated biomass at optimized APO conditions was 177.89 mg equivalent glucose g�1 dry biomass. Addition of 10 bar air pressure at the optimized pretreatment conditions increased the sugars yield to 263.49 mg equivalent glucose g�1 dry biomass

Optimization of pretreatment conditions using full factorial design and enzymatic convertibility of shea tree sawdust

In this study alkaline wet air oxidation (WAO), alkaline peroxide assisted wet air oxidation (APAWAO), and enzymatic hydrolysis methods were evaluated for conversion of wood residue (sawdust) to reducing sugars. Cellulose content, hemicellulose solubilization, and lignin removal forWAOpretreatment conditions were optimized by statistical analysis using a 23-full factorial design with reaction temperature, air pressure, and reaction time as the process parameters. An optimum WAO condition of 170 �C, 1.0 MPa, 10 min was predicted and experimentally validated to give 518 g kg-1 cellulose content, 580 g kg-1 hemicellulose solubilization, and 171 g kg-1 lignin removal in the solid fraction. About 7 g L-1 reducing sugars was detected in the pretreated liquid fraction. Presoaking the dry raw biomass for 24 h in H2O2 followed by wet air oxidation (APAWAO) at the optimized conditions resulted in enrichment up to 683 g kg-1 cellulose content in the solid fraction along with solubilization of 789 g kg-1 hemicellulose and 280 g kg-1 lignin removal. The yield of reducing sugars from WAO optimized conditions by two enzyme preparations (cellulase and b-glucosidase) was 131mgg-1 of dry substrate, while the APAWAO yielded 274mgg-1. Pretreatments used in this study showed to have a disrupting effect on the lignocellulosic biomass, making the treated materials accessible for enzymatic hydrolysis. The combination of presoaking inH2O2 before WAO pretreatment and enzymatic hydrolysis was found to give the highest sugar yield

Treatment of waste gas containing diethyldisulphide (DEDS) in a bench scale biofilter

Waste gas containing diethyldisulphide (DEDS) is generated from various industries including pulp and paper, refinery, rayon and molasses based distilleries, etc. DEDS has odour threshold detection with an average concentration of 10�9 mg/m3 at 25 �C. DEDS is toxic to bacteria, fungus and also to mammals when exposed for a long period. Waste gas containing DEDS require proper treatment prior to discharge into the environment. DEDS containing waste gas was treated in a biofilter, packed with compost along with wooden chips and enriched with DEDS degrading microorganisms. The biofilter could remove DEDS to the extent of 94 ± 5% at a loading of 1.60 g/m3/h with an empty bed retention time of 150 s. At optimal operating conditions, the average moisture content required by the biofilter was in the range of 60–65%. The biodegradative products of DEDS were thiosulphate and sulphate

Treatment of waste gas containing low concentration of dimethyl sulphide in a high performance biotrickling filter

1018-1023A bench-scale biotrickling filter was operated in the laboratory for the treatment of dimethyl sulphide (DMS). The biotrickling filter was packed with pre-sterilized polyurethane foam and seeded with biomass developed from garden soil enriched with DMS. The biotrickling filter was operated for the generation of process parameters. The biotrickling filter could remove an average removal efficiency of 40.95 % at an effective bed contact time of 84 sec with an average loading rate of 0.56 mg/m3/h. Evaluation of microbiological status of the biotrickling filter indicated the presence of other bacterial cultures viz. Paenibacillus polymyxa, and Bacillus megaterium, besides Bacillus sphaericus.</i

Production of biodegradable plastics from activated sludge generated from a food processing industrial wastewater treatment plant

Most of the excess sludge from a wastewater treatment plant (60%) is disposed by landfill. As a resource utilization of excess sludge, the production of biodegradable plastics using the sludge has been proposed. Storage polymers in bacterial cells can be extracted and used as biodegradable plastics. However, widespread applications have been limited by high production cost. In the present study, activated sludge bacteria in a conventional wastewater treatment system were induced, by controlling the carbon: nitrogen ratio to accumulate storage polymers. Polymer yield increased to a maximum 33% of biomass (w/w) when the C/N ratio was increased from 24 to 144, where as specific growth yield decreased with increasing C/N ratio. The conditions which are required for the maximum polymer accumulation were optimized and are discussed

Growth and biochemical response of an indigenous oleaginous microalga <em>Scenedesmus obtusus</em> cultivated in outdoor open ponds

40-49Understanding the response of microalgae to outdoor culture conditions is necessary for the development of large open pond cultivation system for various value added applications. In this context, we evaluated the response of an indigenous oleaginous green microalga Scenedesmus obtusus CFR 1-09/FW to outdoor culture conditions. The microalga was cultivated in open ponds at various culture depths under nutrient replete condition. The pond with 3 cm culture depth showed highest biomass productivity (49.05±11.74 mg L-1 day-1). The high surface solar irradiance (1831 µmol m-2 s-1) led to a decrease in chlorophyll content (from 12.21 to 4 µg mg-1). The long duration exposure to lower temperatures (≤20°C) during night led to an increase in poly unsaturated fatty acids (PUFAs) content (47.21±2.83% w/w mass fraction of FAME). The omega-3 alpha linolenic acid (ALA) content rose significantly reaching 31.01±3.79% (w/w) mass fraction of FAME. The high content of carbohydrate (23.4±0.64% w/w), protein (37.62 ± 2.15% w/w), lipid (21.55±1.43% w/w), palmitic acid (30.97±4.02% w/w mass fraction of FAME) and ALA in outdoor cultures makes this microalga a potential candidate for outdoor cultivation for food and feed applications. The study provides valuable insights for developing outdoor open pond cultivation protocol

pyridine biodegradation in a novel rotating rope bioreactor

A novel immobilised bioreactor has been developed especially for the treatment of pollutants characterized by high volatility alongwith high water solubility and low microbial yields. The new bioreactor referred to as the rotating rope bioreactor (RRB) provides higher interfacial area (per unit reactor liquid volume) along with high oxygen mass transfer rate, greater microbial culture stability; and consequently higher substrate loadings and removal rates in comparison to other conventional rectors for the treatment of volatile compounds. Pyridine was used as a model compound to demonstrate the enhanced performance with RRB, when compared to that reported with other conventional bioreactors. The experimental results indicate that the novel RRB system is able to degrade pyridine with removal efficiency of more than 85% at higher pyridine concentration (up to 1000 mg/l) and loading [up to 400 mg/m2/h (66.86 g/ m3/h)], with a shorter hydraulic retention time (9–18 h). The reactor has been in operation for the past 15 months and no loss of activity has been observed