Pradeep Verma

An overview of key pretreatment processes employed for bioconversion of lignocellulosic biomass into biofuels and value added products

The hunt for alternative sources of energy generation that are inexpensive, ecofriendly, renewable and can replace fossil fuels is on, owing to the increasing demands of energy. One approach in this direction is the conversion of plant residues into biofuels wherein lignocellulose, which forms the structural framework of plants consisting of cellulose, hemicellulose and lignin, is first broken down and hydrolyzed into simple fermentable sugars, which upon fermentation form biofuels such as ethanol. A major bottleneck is to disarray lignin which is present as a protective covering and makes cellulose and hemicellulose recalcitrant to enzymatic hydrolysis. A number of biomass deconstruction or pretreatment processes (physical, chemical and biological) have been used to break the structural framework of plants and depolymerize lignin. This review surveys and discusses some major pretreatment processes pertaining to the pretreatment of plant biomass, which are used for the production of biofuels and other value added products. The emphasis is given on processes that provide maximum amount of sugars, which are subsequently used for the production of biofuels.

Microbial fuel cell: a green approach for the utilization of waste for the generation of bioelectricity

Today we are witnessing a global energy crisis due to huge energy demands and limited resources. Non-renewable energy sources are depleting and renewable energy sources are not properly utilized. There is an immediate need for search of alternate routes for energy generation. Microbial fuel cell (MFC) technology, which uses microorganisms to transform chemical energy of organic compounds into electricity is considered a promising alternative. Extensive studies have corroborated new insights into MFC, which show that a wide array of carbon sources including wastes can be employed using a variety of microbes. Consequently, microbial transformation of wastes using novel bioremediation strategies such as MFC for energy generation is considered as an efficient and environmentally benign approach. This paper deals with critical review of different classes of xenobiotics and wastes that can be employed for bioenergy generation, microorganisms involved, power output, major benefits, challenges and pit holes of MFC technology.

Metabolism of Chicken Feathers and Concomitant Electricity Generation by Pseudomonas aeruginosa by Employing Microbial Fuel Cell (MFC)

Keratinolytic potential of Pseudomonas aeruginosa strain SDS3 has been evaluated for the metabolism of chicken feathers. Results indicated that strain SDS3 showed complete metabolism of 0.1 and 0.5% (w/v) chicken feathers in minimal medium. Feathers were metabolized up to 80% at 1% (w/v) concentration. Maximum soluble protein ( μg/mL) and keratinase ( U/mL) were observed in the presence of 1% chicken feathers after five days of incubation. The effect of carbon and nitrogen sources showed that feather degradation was stimulated by complex carbon/nitrogen sources such as starch, malt extract, tryptone, and beef extract and was inhibited by simple carbon and nitrogen sources. Electricity production by employing chicken feathers as a substrate in microbial fuel cell (MFC) was evaluated. It was observed that maximum voltage corresponding to 141 mV was observed after 14 days of incubation. Maximum power density of 1206.78 mW/m2 and maximum current density of 8.6 mA/m2 were observed. The results clearly indicate that chicken feathers can be successfully employed as a cheap substrate for electricity production in MFC. This is the first report showing employment of chicken feathers as substrate in MFC.

An Integrated Approach of Using Polystyrene Foam as an Attachment System for Growth of Mixed Culture of Cyanobacteria with Concomitant Treatment of Copper Mine Waste Water

Cyanobacteria have tremendous applications in areas such as production of biofuels and pharmaceutically important pigments and are used as an adsorbent for the removal of toxic metabolites. However, large scale production of Cyanobacteria is not economically feasible due to high cost involved in separation of biomass. In this context, different attachment systems have been developed for the growth of Cyanobacteria on a solid support. In this study, a simple and economical attachment system using polystyrene foam for growth of Cyanobacteria has been presented. Results clearly indicate that high biomass yield can be obtained in attached system when compared to suspended system. In attachment system, the biomass yield showed 21.4%, total protein content showed 29.2%, chlorophyll content showed 11.1%, and carotenoid content showed 13.1% increase as compared to the suspended system. The attachment system can also support the growth of Cyanobacteria in presence of copper mine waste water with concomitant removal of copper ions. These results were corroborated by COD analysis, which indicated significant reduction. Further, copper removal was high in attached system as compared to suspended system. It appears that attachment system offers protection for growing Cyanobacteria and can be effectively employed for growing Cyanobacteria in presence of waste water coming from different sources.

Advances in Concurrent Bioelectricity Generation and Bioremediation Through Microbial Fuel Cells

Increasing population, industrialization and urbanization has led to two most persistent problems for modern world, i.e. energy crisis and waste disposal. Microbial fuel cell (MFC) has emerged as a technique for the generation of electricity under the influence of the metabolic action of microbes. The technique is known since 100 years, but in the last two decades, the research group have shown keen interest in this technique as it is capable of solving energy crisis and waste management. Researchers have designed several types of MFCs which are capable of utilizing several waste materials such as lignocellulose biomass, toxic chemicals, polluted sediment soils, sewage sludge and petroleum hydrocarbons, etc. The substrate can be used under the influence of large group of microbes for generating energy which can be harnessed to meet the growing energy demand. In present the efforts of several research groups and technological advancement has made this technology affordable and cost-effective. This chapter focus on presenting recent technological developments in the MFC for concurrent bioelectricity generation and bioremediation with special focus on type of electrodes materials, substrates and various designs of MFC used for bioremediation. It also gives an insight into the economic feasibility of the technique for commercialization and future prospect of the technology.

Purification and characterization of a thermo-acid/alkali stable xylanases from Aspergillus oryzae LC1 and its application in Xylo-oligosaccharides production from lignocellulosic agricultural wastes

Xylooligosaccharides (XOS) from lignocellulosic biomass (LCB) have found widespread applications in food, feed, nutraceuticals and pharamecutical industries. Enzymatic degradation of LCB for generation of XOS have gained impetus in recent times In the present investigation an extracellular thermo-alkali stable xylanase from Aspergillus oryzae LC1 was purified by using PEG 8000/MgSO4 aqueous two-phase system and was capable of hydrolysing various agricultural residues into XOS system. Highest activity was observed using 11.3% (w/w) PEG 8000 and 22.5% (w/w) sulphate salt with maximum purification factor (13-fold), highest yield (86.8%) and partition coefficient (8.8%). The purification of the crude enzyme also resulted in decrement of β-xylosidase activity (29.8 U/mL to 0.6 U/mL). The molecular weight of enzyme was estimated ~35 kDa. The highest residual activity was obtained with birch wood xylan as substrate with Km and Vmax of 0.2 mg/mL and 172.2 μmol min-1 mg-1 respectively. The metal ions Fe2+, Ag2+, Mg2+, Mn+ and Co+ enhanced xylanase activity while EDTA, DMSO and SDS acted as inhibitor. The effect of Fe+2 was confirmed by the circular dichroism experiment. The partially purified enzyme was capable of generating XOS i.e. xylobiose (0.68 mg/g), xylotriose (2.47 mg/g) and xylotetraose (2.29 mg/g) by direct enzymatic hydrolysis of untreated sugarcane baggase, wheat straw and wheat bran respectively.

Fungal laccase discovered but yet undiscovered

Laccases belongs to multinuclear copper-containing oxidase and can act on a variety of aromatic and non-aromatic compounds. Due to their broad substrate specificity, they are considered as a promising candidate in various industrial and biotechnological sectors. They are regarded as a “Green Tool”/“Green Catalyst” in biotechnology. The present review focuses on structure, reaction mechanism, categories, applications, economic feasibility, limitations, and future prospects of fungal laccases. Thus, this review would help in understanding laccases along with the areas, which has not been focused and requires attention. Since past, immense work has been carried out on laccases: yet, new discoveries and application are ever increasing which includes bio-fuel, bio-sensor, fiber board synthesis, bioremediation, clinical, textile industry, food, cosmetics, and many more. Hence, it can be stated that fungal laccase is an enzyme which is “discovered but yet undiscovered”.

A Comparative Assessment of Autoclave and Microwave-Assisted Peroxometal Complex in Delignification of Wood Biomass for Enhanced Sugar Production

For production of biofuels from woody biomass, an initial pretreatment step is required for removal of lignin prior to enzymatic saccharification. In the present study, ameliorating effects of peroxometal complexes on delignification of beech wood have been studied using external (autoclave) heating and microwave irradiation. The results clearly show that ammonium molybdate, when transformed to peroxometal complex by hydrogen peroxide (H2O2), exhibits potent delignification property. The beech wood gave sugar yield of 69 and 41.8% after microwave irradiation and autoclave heating, respectively, under optimized conditions. The results indicate that maximum sugar yield depends upon delignification of biomass as lignin inhibits conversion of cellulose into sugars. It can be concluded that excellent delignifying capability of the H2O2-activated ammonium molybdate system can be achieved through microwave radiation.