Search

This paper focuses on the use of Cyclea peltata leaf extract for green synthesis of silver nanoparticles (CPL-AgNPs) post-optimization by one variable at a time (OVAT) approach for nonlinear optics application. The leaf extract of Cyclea peltata (10% w/v) and AgNO3 (1 mM) was used for the synthesis of silver nanoparticles (CPL-AgNPs). Reactions conditions like CPL extract concentration, salt concentration, temperature, pH, RPM, and time for synthesis were optimized by using OVAT approach. A UV-visible spectroscopic investigation confirmed the biosynthesis of CPL-AgNPs at 420 nm. Field emission scanning electron microscope (FESEM) confirmed the spherical monodispersed nanoparticles in the range of 30–50 nm and EDAX confirmed the purity of the sample. FTIR confirmed the capping of nanoparticles by plant phytochemicals. The synthesized CPL-AgNPs were evaluated for nonlinear optical properties using the Z-scan technique at 532 nm with a CW laser. Strong nonlinear absorption by the nanoparticles in the range of 2.85 × 10−2 cm/W was observed. Moreover, CPL-AgNPs display superior optical limitations.

The objective of the present study was to optimise the biosynthesis of gold nanoparticles using aqueous extract of Pongamia seed cake (PSC). Proteins, amino acids and phenolic compounds present in the PSC extract are responsible for reducing the metal precursor salt to nanoparticles. The levels of factors for optimisation of nanoparticles synthesis was evaluated using UV–Vis spectrophotometer by one factor at a time studies. Further factorial design was employed to study the significant effect of various parameters on the nanoparticles synthesis. The levels of two significant factors i.e. pH and concentration of PSC extract as obtained from factorial design were optimized further for maximum nanoparticle synthesis applying central composite design. The optimized conditions were found to be pH 3.6 and PSC extract concentration of 17.07% (w/v) at which an increase (OD at 530 nm = 1.3) in nanoparticle synthesis was observed as compared to un-optimized conditions (OD at 530 nm = 0.66). The model obtained on optimization was validated and it describes the nanoparticle synthesis aptly with an error between experimental and predicted values of just 1.15% with an R2 of 0.985. It can be concluded that, RSM approach was found to be an efficient technique to optimize the reaction conditions, where a twofold increase in synthesis of small sized monodispersed gold nanoparticles was seen.

Enterococcus durans NCIM5427 (ED-27), capable of producing an intracellular acid stable lipase, was isolated from fish processing waste. Its growth and subsequent lipase production was optimized by Box Behneken design (optimized conditions: 5 % v/v fish waste oil (FWO), 0.10 mg/ml fish waste protein hydrolysates (FWPH) at 48 h of fermentation time). Under optimized conditions, ED-27 showed a 3.0 fold increase (207.6 U/ml to 612.53 U/ml) in lipase production, as compared to un-optimized conditions. Cell growth and lipase production was modeled using Logistic and Luedeking-Piret model, respectively; and lipase production by ED-27 was found to be growth-associated. Lipase produced by ED-27 showed stability at low pH ranges from 2 to 5 with its optimal activity at 30 °C , pH 4.6; showed metal ion dependent activity wherein its catalytic activity was activated by barium, sodium, lithium and potassium (10 mM); reduced by calcium and magnesium (10 mM). However, iron and mercury (5 mM) completely inactivated the enzyme. In addition, modifying agents like SDS, DTT, β-ME (1%v/v) increased activity of lipase of ED-27; while, PMSF, DEPC and ascorbic acid resulted in a marked decrease. ED-27 had maximum cell growth of 9.90309 log CFU/ml under optimized conditions as compared to 13 log CFU/ml in MRS. The lipase produced has potential application in poultry and slaughterhouse waste management.

Enterococcus faecium MTCC 5695 possessing potential probiotic properties as well as enterocin producing ability was used as starter culture. Effect of time (12–24 h) and inoculum level (3–7 % v/v) on cell growth, bacteriocin production, antioxidant property, titrable acidity and pH of curd was studied by response surface methodology (RSM). The optimized conditions were 26.48 h and 2.17%v/v inoculum and the second order model validated. Co cultivation studies revealed that the formulated product had the ability to prevent growth of foodborne pathogens that affect keeping quality of the product during storage. The results indicated that application of E. faecium MTCC 5695 along with usage of optimized conditions attributed to the formation of highly consistent well set curd with bioactive and bioprotective properties. Formulated curd with potential probiotic attributes can be used as therapeutic agent for the treatment of foodborne diseases like Traveler’s diarrhea and gastroenteritis which thereby help in improvement of bowel health.