366
N. B. Raj et al.
4 Current Challenges
The greatest challenge in using microbial-based NPs is the state of reproducibility.
Genetic instability and various stress response encountered by a microbial cell may
lead to differences in the composition, reproducibility and yield in the nanoparticle
synthesis. Further, growing lines of evidences support existence of a vast difference
within the microbial species toward nanoparticle synthesis. Optimization of ideal
conditions is understudied for microbial growth as well as sample preparation and
processing, which are prerequisite to maintain homogeneity. Efficient control of size,
shape and dispersity of nanoparticle still remains unanswered. Comprehensive field
trials are essential to comprehend the nanotoxicity in plants regarding uptake and
translocation of nanoparticles by plants and effect of the NPs in the rhizosphere and on
root surfaces. Nanoparticles may also interact with non-targeted plants causing undesirable outcomes. Influence of NPs on beneficial microorganisms, water eco-system,
animals, birds, insects, human and environment remains untapped area. Toxicity
residues and biotransformed products of NPs in plants, plant-based products and in
the soil are not yet well studied. Awareness to the general public and to policy makers
regarding the possible outcomes of application of microbial nanotechnology is still
lacking. These factors at the moment limit the applications of microbe-mediated
nanoparticles for various applications in agriculture.
5 Future Prospects
The convergence of chemistry, material engineering and microorganisms is considered as futuristic approach for eco-friendly nanoparticle synthesis. Globally, tremendous developments have been advanced in the field of microbial nanotechnology,
and their applications in myriad areas in general and agriculture sector, which is the
backbone of the developing nation like India in particular, are explored incessantly.
Nevertheless, there are certain gaps and limitations in designing optimum synthesis
of nanoparticles which need to be solved by the scientific community. Maximum
productivity can be achieved by optimizing various biological, physical and chemical parameters such as type of microorganism used, enzyme concentration, protein
concentration, inoculum age, pH, temperature, concentration of metal ions, culture
medium and reaction time among others.
Another relatively unexplored area is mechanism of microbial-mediated nanoparticle synthesis. Thus, more exhaustive investigations are warranted to outline
the mechanism, proteins, enzymes and other factors involved in the nanoparticle
synthesis. At present, only few types of NPs such as Au, Ag, CdS, Zr, Mg, Pt,
Pd, Se, Zn, Cu, Fe and Ti are being synthesized from microbial sources. Hence,
other types of NP synthesis through biological route must be encouraged. Many
reports suggest that, among the microbial world, fungi are more explored for NPs
synthesis. Therefore, unmapped microbial cell factories from various sources such as
N. B. Raj et al.
4 Current Challenges
The greatest challenge in using microbial-based NPs is the state of reproducibility.
Genetic instability and various stress response encountered by a microbial cell may
lead to differences in the composition, reproducibility and yield in the nanoparticle
synthesis. Further, growing lines of evidences support existence of a vast difference
within the microbial species toward nanoparticle synthesis. Optimization of ideal
conditions is understudied for microbial growth as well as sample preparation and
processing, which are prerequisite to maintain homogeneity. Efficient control of size,
shape and dispersity of nanoparticle still remains unanswered. Comprehensive field
trials are essential to comprehend the nanotoxicity in plants regarding uptake and
translocation of nanoparticles by plants and effect of the NPs in the rhizosphere and on
root surfaces. Nanoparticles may also interact with non-targeted plants causing undesirable outcomes. Influence of NPs on beneficial microorganisms, water eco-system,
animals, birds, insects, human and environment remains untapped area. Toxicity
residues and biotransformed products of NPs in plants, plant-based products and in
the soil are not yet well studied. Awareness to the general public and to policy makers
regarding the possible outcomes of application of microbial nanotechnology is still
lacking. These factors at the moment limit the applications of microbe-mediated
nanoparticles for various applications in agriculture.
5 Future Prospects
The convergence of chemistry, material engineering and microorganisms is considered as futuristic approach for eco-friendly nanoparticle synthesis. Globally, tremendous developments have been advanced in the field of microbial nanotechnology,
and their applications in myriad areas in general and agriculture sector, which is the
backbone of the developing nation like India in particular, are explored incessantly.
Nevertheless, there are certain gaps and limitations in designing optimum synthesis
of nanoparticles which need to be solved by the scientific community. Maximum
productivity can be achieved by optimizing various biological, physical and chemical parameters such as type of microorganism used, enzyme concentration, protein
concentration, inoculum age, pH, temperature, concentration of metal ions, culture
medium and reaction time among others.
Another relatively unexplored area is mechanism of microbial-mediated nanoparticle synthesis. Thus, more exhaustive investigations are warranted to outline
the mechanism, proteins, enzymes and other factors involved in the nanoparticle
synthesis. At present, only few types of NPs such as Au, Ag, CdS, Zr, Mg, Pt,
Pd, Se, Zn, Cu, Fe and Ti are being synthesized from microbial sources. Hence,
other types of NP synthesis through biological route must be encouraged. Many
reports suggest that, among the microbial world, fungi are more explored for NPs
synthesis. Therefore, unmapped microbial cell factories from various sources such as