Anita Singh

Enhanced saccharification of rice straw and hull by microwave–alkali pretreatment and lignocellulolytic enzyme production

In this study, statistical design of experiments was employed to plan experiments and optimize the microwave-alkali pretreatment of rice straw and hulls. Process parameters important in pretreatment of biomass were identified by a Plackett-Burman design and the parameters with significant effects were optimized using a box-behnken design (BBD). Experimental results show that alkali concentration (AC), irradiation time (IT) and substrate concentration (SC) were main factors governing the saccharification of rice straw and hulls. Optimum conditions of pretreatment were AC 2.75%, IT 22.50 min and SC 30 g/L, as optimized by BBD. The growth and production of lignocellulolytic enzymes from Aspergillus heteromorphus, solid state fermentation (SSF) was performed using rice straw and hulls pretreated under optimum conditions. Cellulases and xylanase reached the highest enzyme activity at 6th day of fermentation while maximum manganese peroxidase (MnP) and laccase activity occurred at 12th day.

Enzymatic hydrolysis optimization of microwave alkali pretreated wheat straw and ethanol production by yeast

Microwave alkali pretreated wheat straw was used for in-house enzyme production by Aspergillusflavus and Trichodermareesei. Produced enzymes were concentrated, pooled and assessed for the hydrolysis of pretreated wheat straw. Factors affecting hydrolysis were screened out by Placket-Burman design (PBD) and most significant factors were further optimized by Box-Behnken design (BBD). Under optimum conditions, 82% efficiency in hydrolysis yield was observed. After the optimization by response surface methodology (RSM), a model was proposed to predict the optimum value confirmed by the experimental results. The concentrated enzymatic hydrolyzate was fermented for ethanol production by Saccharomyces cerevisiae, Pichia stipitis and co-culture of both. The yield of ethanol was found to be 0.48 g(p)/g(s), 0.43 g(p)/g(s) and 0.40 g(p)/g(s) by S. cerevisiae, P. stipitis and by co-culture, respectively, using concentrated enzymatic hydrolyzate. During anaerobic fermentation 42.31 μmol/mL, 36.69 μmol/mL, 43.35 μmol/mL CO(2) was released by S. cerevisiae, P. stipitis and by co-culture, respectively.

LACCASE PRODUCTION BY ASPERGILLUS HETEROMORPHUS USING DISTILLERY SPENT WASH AND LIGNOCELLULOSIC BIOMASS

Laccase is among the major enzymes which plays an important role in ligninolytic system of fungi. Laccase production by Aspergillus heteromorphus was studied using anaerobically treated distillery spent wash (ADSW) and lignocellulosic biomass. Lignocellulosic biomass (rice straw, wheat straw and sugarcane bagasse) generated during biomass processing leads to solid waste and distillery spent wash is unwanted liquid waste produced by distilleries, both causes environmental pollution. Two mineral media and anaerobically treated distillery spent wash medium was tested for laccase production. Enzyme production in various media and in presence and absence of lignocellulosic biomass supplements showed that anaerobically treated distillery spent wash medium was a better laccase inducer medium than the mineral media. Addition of lignocellulosic biomass enhances laccase production and highest laccase activity was obtained in 5% anaerobically treated distillery spent wash medium with rice straw.

Physico-chemical pretreatment and enzymatic hydrolysis of cotton stalk for ethanol production by Saccharomyces cerevisiae

The aim of this work was to study the physico-chemical pretreatment and enzymatic hydrolysis of cotton stalk for ethanol production by Saccharomyces cerevisiae. Firstly, factors affecting pretreatment were screened out by Plackett-Burman design (PBD) and most significant factors were further optimized by Box-Behnken design (BBD). As shown by experimental study, most significant factors were FeCl3 concentration (FC), irradiation time (IT) and substrate concentration (SC) affecting pretreatment of cotton stalk among all studied factors. Under optimum conditions of pretreatment FC 0.15mol/l, IT 20min and SC 55g/l, the release of reducing sugar was 6.6g/l. Hydrolysis of pretreated cotton stalk was done by crude on-site produced enzymes and hydrolysate was concentrated. Ethanol production by Saccharomyces cerevisiae using concentrated cotton stalk hydrolysate was 9.8gp/l, with ethanol yield 0.37gp/gs on consumed sugars. The data indicated that microwave FeCl3 pretreated cotton stalk hydrolyses by crude unprocessed enzyme cocktail was good, and ethanol can be produced by fermentation of hydrolysate.

Evaluation and statistical optimization of methane oxidation using rice husk amended dumpsite soil as biocover.

A laboratory scale study was conducted to investigate the effect of rice husk amended biocover to mitigate the CH4 emission from landfills. Various physico-chemical and environmental variables like proportion of amended biocover material (rice husk), temperature, moisture content, CH4 concentration, CO2 concentration, O2 concentration and incubation time were considered in the study which affect the CH4 bio-oxidation. For the present study, sequential statistical approach with Placket Burman Design (PBD) was used to identify significant variables, having influential role on CH4 bio-oxidation, from all variables. Further, interactive effect of four selected variables including rice husk proportion, temperature, CH4 concentration and incubation time was studied with Box-Behnken Design (BBD) adopting Response Surface Methodology (RSM) to optimize the conditions for CH4 oxidation. In this study, the maximum CH4 oxidation potential of 76.83μgCH4g(-1)dwh(-1) was observed under optimum conditions with rice husk amendment of 6% (w/w), 5h incubation time at 40°C temperature with 40% (v/v) initial CH4 concentration. The results for CH4 oxidation potential also advocated the suitability of rice husk amendment in biocover system to curb emitted CH4 from landfills/open dumpsite over conventional clay or sand cover on supplying CH4 and O2 to microbes on maintaining proper aeration.

Statistical assessment of dumpsite soil suitability to enhance methane bio-oxidation under interactive influence of substrates and temperature

Biocovers are considered as the most effective and efficient way to treat methane (CH4) emission from dumpsites and landfills. Active methanotrophs in the biocovers play a crucial role in reduction of emissions through microbiological methane oxidation. Several factors affecting methane bio-oxidation (MOX) have been well documented, however, their interactive effect on the oxidation process needs to be explored. Therefore, the present study was undertaken to investigate the suitability of a dumpsite soil to be employed as biocover, under the influence of substrate concentrations (CH4 and O2) and temperature at variable incubation periods. Statistical design matrix of Response Surface Methodology (RSM) revealed that MOX rate up to 69.58μgCH4g-1dwh-1 could be achieved under optimum conditions. MOX was found to be more dependent on CH4 concentration at higher level (30-40%, v/v), in comparison to O2 concentration. However, unlike other studies MOX was found in direct proportionality relationship with temperature within a range of 25-35°C. The results obtained with the dumpsite soil biocover open up a new possibility to provide improved, sustained and environmental friendly systems to control even high CH4 emissions from the waste sector.