Ambalal Chaudhari

Thermophilic anaerobic digestion: the best option for waste treatment.

After introducing thermophilic anaerobic digestion (AD), characteristics of thermophilic methanogens are provided. Accordingly, (a) site of occurrence, (b) morphological characteristics (shape and motility), (c) biochemical characteristics (Gram character and % G+C profile), (d) nutritional characteristics (NaCl requirement and substrate specificity), and (e) growth characteristics (pH and temperature) of thermophilic methanogens are described. Some studies of the thermophilic AD are cited with their operational management problems. Subsequently, strategies to maximize net energy production are given, including mode of heating the bioreactors, role of agitation to promote AD performance and mode/intensity of mixing. Finally, advantages as well as drawbacks of AD under thermophilic conditions are given, concluding with its applications.

Ultrasound-assisted/biosurfactant-templated size-tunable synthesis of nano-calcium sulfate with controllable crystal morphology.

Nano-sized crystals of alpha calcium sulfate hemihydrate (α-HH) with considerable morphology-dependent properties find promising applications in the clinical fields as a cementitious material. Towards this end, ultrasound-assisted rhamnolipid and surfactin biosurfactant-template route is explored to control the morphology and aspect ratio of nano-CaSO4 by adjusting the mass ratio of rhamnolipid/H2O, surfactin/H2O and rhamnolipid/surfactin. The change in the molar ratio of [SO4(2-)]:[Ca(2+)] results in modification in variable morphology and size of nano-CaSO4 including long, short rods and nanoplates. With increase in the rhamnolipid/H2O ratio from 1.3 to 4.5, the crystal length decreases from 3 μm to 600 nm with the corresponding aspect ratio reduced sharply from 10 to 3. Similarly, the crystal morphology gradually changes from submicrometer-sized long rod to hexagonal plate, and then plate-like appearance with increase in surfactin concentration. The preferential adsorption of rhamnolipid on the side facets and surfactin on the top facets contributes to the morphology control. The process using 50% amplitude with a power input of 45.5 W was found to be the most ideal as observed from the high yields and lower average l/w aspect ratio, leading to more than 94% energy savings as compared to that utilized by the conventional process. As a morphology and crystal habit modifier, effects of Mg(2+) and K(+) ions on α-HH growth were investigated to find an optimal composition of solution for α-HH preparation. Mg(2+) ions apparently show an accelerating effect on the α-HH growth; however, the nucleation of α-HH is probably retarded by K(+) ions. Thus, the present work is a simple, versatile, highly efficient approach to controlling the morphology of α-HH and thereby, offers more opportunities for α-HH multiple applications.

Extracellular biosynthesis of zinc oxide nanoparticles using Rhodococcus pyridinivorans NT2: Multifunctional textile finishing, biosafety evaluation and in vitro drug delivery in colon carcinoma

In this study, zinc oxide (ZnO) nanoparticles (NPs) were rapidly synthesized from zinc sulfate solution at room temperature using a metabolically versatile actinobacteria Rhodococcus pyridinivorans NT2. The morphology, structure and stability of the synthesized ZnO NPs were studied using UV-visible absorption spectroscopy, X-ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), Zeta potential, and thermogravimetry. The data indicated that the synthesized nanoparticles were moderately stable, hexagonal phase, roughly spherical with average particle diameter in the range of 100-120 nm. Results obtained on examination of protein expression revealed that cell enzymes and extracellular protein systems of Rhodococcus sp. may take part in synthesis process. Furthermore, the ZnO NPs were coated onto textile fabrics to enhance UV-blocking, self-cleaning and antibacterial properties. Ultraviolet protecting factor (UPF) indicating UV-blocking properties of ZnO NPs coated textile fabrics were determined as 65, 88, 121, 172 and 241 for 1, 2, 3, 4 and 5 gm(-2) of ZnO NPs, respectively. Besides, self-cleaning activity was assessed by investigating photocatalytic activity on malachite green as well as antibacterial activity against aerobic Gram-positive Staphylococcus epidermidis NCIM 2493 (ATCC 12228). The antibacterial effects of these textiles were evaluated using ISO 20743 standard. In addition, ZnO NPs exhibited a preferential ability to kill HT-29 cancerous cells as compared with normal peripheral blood mononuclear cells (PBMCs).

Novel Tensio-Active Microbial Compounds for Biocontrol Applications

Several microorganisms are known to produce tensio-active compounds (biosurfactants). They have emerged out as successful alternative to synthetic surfactants. The enormous diversity of biosurfactants makes them interesting for application in several areas. Rhamnolipids are one such heterogeneous group of compounds which has been studied as a model system and acquired a status as potential performance-effective molecules in various fields, like production of speciality chemicals, additives for environmental remediation and biological control agent.

Mesophilic anaerobic digestion: first option for waste treatment in tropical regions

Rural India derives its energy needs for cooking and heating through the use of fuel wood and for lighting and agricultural operations through kerosene and diesel. Use of fuel wood has aggravated the problem of de-forestation, while availability of kerosene and diesel cannot be guaranteed due to corrupt practices in the public distribution systems. In contrast, urban India derives its energy needs through LPG cylinders, petrol, and electricity. However, their cost and uncertainty rendered them beyond the reach of lower income population. This scenario is more or less true with many developing countries. To meet these objectives, biogas generation from biodegradable waste using anaerobic digestion (AD) appears to be a sustainable avenue as it could be used for (a) water and space heating of farmhouses, animal shelters, (b) generating steam for food processing plants, and (c) electricity generation, in addition to reducing the pollution/hazard potential of these wastes. Many of the underdeveloped and developing countries are in the temperate zone and thus mesophilic AD could provide a desired pathway to achieve a long delayed need of energy for comfortable living, farming, and industrial operations. Efforts made in this direction are reviewed in the present article.

Biosurfactant-Assisted Bioaugmentation in Bioremediation

Surface active compounds (SACs) are basically amphipathic in nature, which alter the properties of fluid interfaces, partition at interface between fluid phases leading to formation of micro-emulsion and impart better wetting, spreading, foaming and detergent traits, thereby rendering them as most versatile process chemicals to be utilized in surfactant-enhanced bioremediation practices. Use of chemical surfactants as an additive, however, warrant (i) toxicity, (ii) carcinogenicity, (iii) non-biodegradibility, (iv) bioaccumulation and (v) inconsistent performance with slow desorption kinetics. Therefore, attention has been focused on alternative amphiphilic surfactants of biological origin, which have predilection for interfaces of dissimilar polarities (liquid-air/liquid-liquid) and are soluble in both organic (non-polar) and aqueous (polar) milieu. The mechanisms of biosurfactant-assisted bioaugmentation in bioremediation include: (i) lowering of interfacial tension, (ii) biosurfactant solubilization of hydrophobic contaminants, and (iii) the phase transfer of pollutants from soil-sorbed to pseudo-aqueous phase. Hence, microbial surfactants have potential attributes as alternative to synthetic surfactants. This article reviews key aspects of microbial tensioactives for applications in bioremediation and biodegradation of environmental pollutants with focus on properties and physiological roles, followed by its laboratory, field demonstrations and full-scale applications. Finally, it is concluded with a concise appraisal on in situ and ex situ biosurfactant-assisted bioaugmentation, along-with impediments and future challenges.

Biodegradation of 2,4-dinitrotoluene with Rhodococcus pyridinivorans NT2: characteristics, kinetic modeling, physiological responses and metabolic pathway

2,4-Dinitrotoluene (2,4-DNT), a major by-product during the synthesis of 2,4,6-trinitrotoluene, is widely used as a gelatinizing, waterproofing and plasticizing agent in explosives and propellants. Since DNTs and its metabolites exhibit toxicity to human beings, fish, algae and microorganisms, they are treated as priority pollutant in several countries. This study describes the biodegradation of 2,4-DNT in batch mode by Rhodococcus pyridinivorans NT2 in the range of 0.5–2 mM. At initial concentration of 0.54 mM, degradation kinetics were described well by zero-order model. However, modeling of the biodegradation at higher concentrations indicated that the Andrews–Haldane model predicts the experimental data fairly well. During growth and biodegradation, changes in saturated/unsaturated ratio of fatty acids, total cyclo fatty acids, and the ratio of anteiso:iso-branching were observed. This was accompanied by increased cell size, alternation in enzymatic and non-enzymatic antioxidant defense systems, accumulation of biosurfactants and carotenoids. Biodegradation of 2,4-DNT by this strain proceeded through a pathway involving intermediates such as 2-amino-4-nitrotoluene and 2,4-diaminotoluene. The strain NT2 harbored plasmid that was found to be associated with biodegradation.

Production of Alkaline Protease by Solvent-Tolerant Alkaliphilic Bacillus circulans MTCC 7942 Isolated from Hydrocarbon Contaminated Habitat: Process Parameters Optimization

In the present investigation, a newly isolated organic solvent-tolerant and alkaliphilic bacterial strain was reported from a hydrocarbon (gasoline and diesel) contaminated soil collected from the petrol station, Shirpur (India). The strain was identified as Bacillus circulans MTCC 7942, based on phenotype, biochemical, and phylogenetic analysis of 16S rRNA gene sequence. The capability of Bacillus circulans to secrete an extracellular, thermostable, alkaline protease and grow in the presence of organic solvents was explored. Bacillus circulans produced maximum alkaline protease (412 U/mL) in optimized medium (g/L): soybean meal, 15; starch, 10; KH2PO4, 1; MgSO4·7H2O, 0.05; CaCl2, 1; Na2CO3, 8; pH 10.0 at 37°C and 100 rpm. The competence of strain to grow in various organic solvents—n-octane, dodecane, n-decane, N,N-dimethylformamide, n-hexane, and dimethyl sulfoxide, establishes its potential as solvent-stable protease source for the possible applications in nonaqueous reactions and fine chemical synthesis.

Detergent-compatible, organic solvent-tolerant alkaline protease from Bacillus circulans MTCC 7942: Purification and characterization.

ABSTRACT Proteases are now recognized as the most indispensable industrial biocatalyst owing to their diverse microbial sources and innovative applications. In the present investigation, a thermostable, organic solvent-tolerant, alkaline serine protease from Bacillus circulans MTCC 7942, was purified and characterized. The protease was purified to 37-fold by a three-step purification scheme with 39% recovery. The optimum pH and temperature for protease was 10 and 60°C, respectively. The apparent molecular mass of the purified enzyme was 43 kD as revealed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The Km and Vmax values using casein-substrate were 3.1 mg/mL and 1.8 µmol/min, respectively. The protease remained stable in the presence of organic solvents with higher (>3.2) log P value (cyclohexane, n-octane, n-hexadecane, n-decane, and n-dodecane), as compared to organic solvents with lower (<3.2) log P value (acetone, butanol, benzene, chloroform, toluene). Remarkably, the protease showed profound stability even in the presence of organic solvents with less log P values (glycerol, dimethyl sulfate [DMSO], p-xylene), indicating the possibility of nonaqueous enzymatic applications. Also, protease activity was improved in the presence of metal ions (Ca2+, Mg2+, Mn2+); enhanced by biosurfactants; hardly affected by bleaching agents, oxidizing agents, and chemical surfactants; and stable in commercial detergents. In addition, a protease–detergent formulation effectively washed out egg and blood stains as compared to detergent alone. The protease was suitable for various commercial applications like processing of gelatinous film and as a compatible additive to detergent formulation with its operative utility in hard water.

Conservation and recycling of pomegranate seeds and shells for value addition

Anaerobic digestion of de-oiled cake of pomegranate seeds (10% SS) has been carried out at 35°C over 240days. It indicated (i) stable pH profile (7.1–7.8), (ii) alkalinity:acidity ratio (6.1–6.8), (iii) healthy volatile fatty acid profile until organic loading rate 3.5, and (iv) biogas production (506l∕kg VS) with maximum 74% methane content. Its scale up to 85m3 has been successfully achieved to replace liquid petroleum gas cylinders for cooking breakfast, lunch, and dinner of about 350 individuals per day, besides use in street lighting. On the other hand, since pomegranate shells showed recalcitrance toward anaerobic digestion, it was composted successfully with and without mixing with banana peels under ambient conditions, 50±5% humidity in 15days by transformation of C:N ratio from 22.5 to 17.0. It provided excellent germination, root ramification, shoot growth, and high chlorophyll content in leaves.