(223b) Biosynthesis of highly stable silver nanoparticles by two distinct strains of Chlamydomonas reinhardtii

Optimizing process parameters for
stable inorganic nanoparticle production in a Multi-Vessel Reactor system using
microalgae

Ashiqur
Rahman¹, Tushar Nemade¹,Shishir Kumar¹,
Adarsh Bafana¹, Si Amar Dahoumane², Clayton Jeffryes^1,3*

¹Nanobiomaterials
and Bioprocessing Laboratory (NABLAB), Dan F. Smith Department of Chemical
Engineering, Lamar University, Beaumont, TX 77710.

²School of Life
Science and Biotechnology, Yachay Tech University, Hacienda San Jose, San
Miguel de Urcuquí, Ecuador.

³Center for Advances in Water & Air Quality,
Lamar University, 211 Redbird Ln. Box
10888, Beaumont, TX 77710-0088, USA

^*Corresponding
author: cjeffryes@lamar.edu

Inorganic
nanoparticles have many applications, including in catalysis, drug delivery and
in biomedical imaging, diagnosis and therapy. Microalgal biosynthesis has been
regarded as a potential process for producing unique types of inorganic
nanoparticles. However, the continuous, self-sustainable mass production of
algal-synthesized NPs remains elusive due to a lack of knowledge about process
parameters. This work uses a Multi-Vessel Reactor (MVR) system to optimize temperatures
and precursor concentrations for such biosynthesis processes. This reactor can
hold up to 34 mini-photobioreactors
(PBR), each provided with air
flow to increase mixing and gas exchange (mainly for the exchange of oxygen and
carbon dioxide) and to keep the algae suspended. In this work silver
nanoparticles (AgNPs) were produced using whole, living cell cultures of Chlamydomonas reinhardtii. Surface
Plasmon Resonance (SPR) excitation in the range of 400–430 nm confirmed the synthesis
of AgNPs. Experiments were done at an approximate
photon flux of 93 ± 7 µmol m^-2
s^-1 with temperatures from 17 °C to 38 °C and AgNO₃
concentration ranging from 0.0125 mM to 1.250 mM. The resultsshowed
that the maximum synthesis of AgNPs took place at 22 °C. The reaction kinetics,
at all concentrations, showed that AgNPs formed in proportion to Ag⁺
concentration indicating that the availability of biological reducing
equivalents were not limiting. The morphological study revealed that the AgNPs
were mostly spherical in shape with mean particle size of 17 ± 13 nm (n = ~250).
The results from this study can be used to further evaluate the parameters that
will lead to a scalable, fully automated, and permanent photobioreactor for the
continuous production of different biogenic inorganic nanoparticles.

Keywords: Multi-Vessel
Reactor, temperature, kinetics, concentration.