CroniconO P E N A C C E S S EC MICROBIOLOGY

Research Article

Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

Abstract

Keywords: Biosynthesis; Silver Nanoparticles; Spectroscopy; Characterization

The biosynthesis of silver nanoparticles extracellularly using baker’s yeast, Saccharomyces cerevisiae was investigated in this study. Biosynthesized silver nanoparticles were characterized by using UV-Visible spectroscopy, which showed a distinct observed absorption peak at 429.00 nm that is attributed to the plasmon resonance of silver nanoparticles; X-ray Diffraction analysis deter-mined the average size of the silver nanoparticle to be ≈ 16.07 nm; the presence of oval shaped silver nanoparticles was determined by scanning electron microscopy (SEM); and Fourier-transform infrared revealed notable peaks at 3332.2, 2903.6, and 1636.3 cm-1 corresponding to the binding of the silver nanoparticles to active biomolecules, alcohols and phenols, carboxylic acids and aromatic amines respectively. The silver nanoparticles were also found to be stable for ninety days. This study supports the use of microorgan-isms as an efficient means of producing silver nanoparticles.

OlobayotanIfeyomi Wilfred* and Bukola Catherine Akin-OsanaiyeDepartment of Microbiology, Faculty of Science, University of Abuja, Abuja, Federal Capital Territory, Nigeria

*Corresponding Author: OlobayotanIfeyomi Wilfred, Department of Microbiology, Faculty of Science, University of Abuja, Abuja, Federal Capital Territory, Nigeria.

Received: June 17, 2019; Published: November 27, 2019

AbbreviationsAgNPs: Silver Nanoparticles; CFE: Cell-Free-Extract; AgNO3: Silver Nitrate; DI: Deionised; OD: Optical Density; nm: Nanometer; μg: Micro-gram; mL: Milliliter; mM: Millimole; a.u: Absorbance Units; UV-VIS: Ultraviolet-Visible; SEM: Scanning Electron Microscope; FT-IR: Fourier Transform-Infrared; XRD: X-ray Diffraction; SPSS: Statistical Package for Social Sciences; ANOVA: Analysis of Variance

IntroductionNanotechnology is the science that deals with matter at the scale of one (1) billionth of a meter (i.e., 10-9 m = 1 nm), and it is also the

study of manipulating matter at the atomic and molecular scale. In general, the size of a nanoparticle spans the range between 1 and 100 nm. Metallic nanoparticles have different physical and chemical properties from bulk metals (e.g. lower melting points, higher specific surface areas, specific optical properties, mechanical strengths, and specific magnetizations), properties that might prove attractive in various industrial applications [1].

Many interesting nanodevices are useful in biomedical field especially for improved cancer detection, diagnosis and treatment [2]. The optical property of the metal is one of the fundamental attractions and a characteristic of a nanoparticle. For example, a 20-nm gold nanoparticle has a characteristic wine red color, a silver nanoparticle is yellowish gray, platinum and palladium nanoparticles are black [3].

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Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

Nanoparticles are nowadays becoming very popular in various fields of research and are useful in combating various diseases help-ing in early and fast detection. These particles in their pure or in the form of mixtures help in the formation of sensors, in batteries, in diagnostic kits, in water treatment, and are also helpful in curing deadly diseases such as cancer. Nanostructure materials show unique physical, chemical, biological and environmental properties, including catalytic activity, optical, electronic and magnetic properties, which have increased their applications in research, engineering, agriculture and medicine [4].

Silver nanoparticles (AgNPs) can be synthesized by physical [5], chemical [6] or biological routes involving plants [7] or microorgan-isms [8]. Biological synthesis is preferred because these methods are safe, cheap, eco-friendly, and do not involve any toxic substrate or by-product [9]. The most common methods for preparing nanoparticles are wet-chemical techniques, which are generally low-cost and high-volume. However, the use of toxic solvents and the contamination from chemicals used in nanoparticle production limit their po-tential use in biomedical applications [10]. Therefore a “green”, non-toxic way of synthesizing metallic nanoparticles is needed in order to allow them to be used in a wider range of industries. This could potentially be achieved by using biological methods. Unlike plants, microbial-mediated synthesis of nanoparticles is not affected by geographical and seasonal variations, avoiding inconsistent morpholo-gies and properties. Microorganisms have short doubling times and represent very suitable producers of nanoparticles, hence, the need to monitor the use of Saccharomyces cerevisiae for the production of silver nanoparticles.

Materials and MethodsMedia preparation and sterilization

The media used was prepared according to manufacturer’s specification. Yeast-extract peptone dextrose was employed for culturing Saccharomyces cerevisiae. A mixture of 0.03g of yeast extract, 0.03g of peptone, 0.1g of dextrose and 2g of agar-agar were dissolved in 100 mL of sterile distilled water. The mixture was boiled using a hotplate while constantly stirring with a sterile glass rod until all the powders were completely dissolved into the solution. The media was sterilized in an autoclave at 121°C and 15 psi for 15 minutes. The media was allowed to cool to about 45°C and 25 mL each was poured into sterile petri dishes where it was allowed to solidify and dry [11].

Collection and preparation of yeast culture

Saccharomyces cerevisiae was grown from commercial baker’s yeast obtained from Osaka Laboratory Equipments, Gwagwalada, Fed-eral Capital Territory and was used for the extracellular synthesis of the silver nanoparticles. The dry seed culture was resuscitated ac-cording to [11]. A stock solution of the baker’s yeast was prepared by dissolving 1g in 50 mL of warm water and then serially diluted (10-1, 10-2, 10-3 and 10-4) in four different sterile test tubes. One ml of the 10-4 dilution of the baker’s yeast broth was inoculated into a growth medium (10mL) containing peptone (0.03g), yeast extract (0.03g), and dextrose (0.1g) and was incubated at 37°C for 48 h after adjusting the pH to 7.0. Two ml of the 48h broth culture was transferred to 100 ml of the production medium of the same composition and the cul-ture was then grown for 48 h at 37°C with constant shaking at 283g. After 48 hours, the cell mass was harvested by centrifugation at 3080 g for 20 minutes (Gallenkamp centrifuge 200). Morphological features of colonies such as colony pigmentation were used for preliminary classification of the fungal population [11].

Synthesis of AgNps and ultraviolet-visible (UV-Vis) spectra analysis

This was carried out according to the method of Kang., et al [12]. The cells of S. cerevisiae were suspended into sterile water (pH 7) and incubated at 30°C and 283g for 72 hours. Cell-free extract (CFE) used for synthesis was collected by passing the supernatant obtained af-ter centrifugation, through a 0.2 μm syringe filter (Pall Corporation, Port Washington, NY, USA). Seven flasks were set up, the first contain-ing 1 mM AgNO3 (HiMedia) without CFE, the second containing only CFE, and the third to seventh flask containing CFE with 1 mM AgNO3

in the ratios 1:25 (1 mL of fungal filtrate with 25 mL of 1 mM AgNO3), 1:50, 1:75, 1:100 and 1:125 respectively, and were incubated at 40°C in static conditions. Synthesis of AgNPs was visually observed for a color change over a period of 168 hours (7 days). Reduction of Ag+ ions was monitored by recording the UV-Vis spectrum between 300 and 800 nm at regular intervals up to 168 hours. The UV-Vis spectra of

93

Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

the solution was recorded using a spectrophotometer “Cary Series UV/Vis” (Agilent Technologies, Germany) with digital data acquisition system, wavelength range (190 - 1100 nm). Silver nanoparticles exhibit striking color (light yellow to brown for silver) due to excitation of surface plasmon vibrations in the particles, and thus provide a convenient means of visually determining their presence in samples [12].

Characterization of silver nanoparticles

The synthesised silver nanoparticles was characterized using UV-Visible spectroscopy to measure optical density at regular intervals; X-ray Diffraction analysis and scanning electron microscopy was done to determine the average size shape of the silver nanoparticles respectively; and Fourier-transform infrared was done to detect the active molecules that are bounded to the silver nanoparticles.

UV-Visible Spectroscopy

The reaction mixture for this test (1 mL of the cell-free-extract of Saccharomyces cerevisiae and 25 mL of silver nitrate solution con-tained in a sterile test tube) was studied using “Cary Series UV/Vis” (Agilent Technologies, Germany) at different incubation times (24, 48, 72, 96, 120, 144 and 168 hours). These measurements were taken at OD of 540 nm [13].

Scanning electron microscopy (SEM)

SEM analysis of the reaction mixture after synthesis of AgNPs was performed according to Khatami., et al. [14] to determine the shape and size of the biosynthesized AgNPs. A drop of the solution containing AgNPs from the UV/Vis analysis was placed on the carbon coated copper films and air-dried without the use of heat. SEM micrograph was taken by a scanning electron microscope (Carl ZIESS, Germany).

X-ray diffraction (XRD)

The XRD pattern of the biosynthesized silver nanoparticles were recorded at room temperature using STOE Stidy-mp (STOE and Cie. GmbH, 134 Darmstadt, Germany) at λ=1.54 Å. For this purpose, colloidal AgNPs was centrifuged (at 1,200 g; 25°C) for 10 minutes, washed by dissolving in deionised (DI) water and recentrifuged. Then the AgNPs was air-dried and subjected to XRD experiment. The X-ray dif-fraction was done in the region of 2θ from 30° to 80°. The AgNPs mean size was calculated by the Debye-Scherrer equation [15]:

D= kλ/βcos θ

In this equation, “D” is the size of crystalline angle, “λ” is the X-ray wavelength (1.54 Å), “θ” is Bragg angle (30° ≤ 2 θ ≤ 80°), “K” is Scherer coefficient between 0.9 - 1, and “β” is the diffraction peak width at half maximum height given in radians.

Fourier Transform - Infrared (FT-IR)

Fourier Transform - Infrared spectral measurements were carried out according to Patil [16] by drying the silver nanoparticles sus-pension in lyophilizer and analyzed by Cary 630 FTIR (Agilent Technologies, Germany) with diffuse reflectance mode in the range of 1000 - 4000 cm-1. This was done to identify the possible interaction between silver and bioactive molecules which may be responsible for synthesis and stabilization of the synthesized silver nanoparticles.

Stability testing

The reduction of the silver ions was monitored over time by UV visible spectral analysis at 540 nm with a quartz curvette and water as a reference. The solution was kept at room temperature over a period of 3 months (90 days). During this period, UV- Vis spectrum of the solution was recorded after every ten days. The color change and the pH of solution were regularly noted to monitor any changes [16].

Statistical analysis

The statistical analyses were carried out using statistical package for social sciences (SPSS). Values of the effect fungal-filtrate con-centration on the synthesis of silver nanoparticles and the stability of the biosynthesized silver nanoparticles were compared using the analysis of variance (ANOVA). For all analyses the level of statistical significance was fixed at p ≤ 0.05.

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Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

ResultsThe colonial morphology of the S. cerevisiae grown on yeast extract-peptone-dextrose medium is shown in figure 1. The colonies were

seen to be oval in shape, flat, of entire margin, cream in colour and opaque. The colonies also gave a positive gram-staining reaction.

Figure 1: Saccharomyces cerevisiae colonies.

There was gradual change in colour of the solution of the mixture of cell free extract and silver nitrate (AgNO3), which signified the synthesis of silver nanoparticles as the number of hours increased and in turn corresponds to increase in optical density readings (Table 1). It also showed that the controls, AgNO3 solution alone and cell free extract alone (0.050 ± 0.0020 and 0.009 ± 0.0010 respectively), relatively had the same optical density readings for the entire 168 hours and was also visibly observed by the non-change of colour over the same period.

From the table, it can be seen that the synthesis of silver nanoparticles was more prominent at the fungal filtrate to silver nitrate ratio of 1:25, which is evident by the colour change from light sky blue to dark brown over a period of 168 hours.

Figure 2 shows a distinct observed absorption peak at 429.00 nm assigned to surface plasmon resonance band of silver nanoparticles indicating its synthesis.

Figure 3 shows the oval shape of the synthesized nanoparticles at x500 magnification as indicated by the arrows.

Figure 4 shows the XRD pattern of the synthesized silver nanoparticles with four prominent peaks found at 2Ɵ = 38.0o, 44.5o, 65.0o and 77.5o, which corresponds to (111), (200), (220), and (311) reflection planes of a face center cubic (FCC) structure of silver. The average size of the nanoparticle was determined as shown in table 2.

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Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

Concentration (µg/mL) Time (Hours) O.D AT 540 nm Colour Change

25

24487296

120144168

0.138 ± 0.00070.201 ± 0.00200.280 ± 0.00150.317 ± 0.00070.519 ± 0.00200.637 ± 0.00100.725 ± 0.0015

-++++

++++

+++

50

24487296

120144168

0.118 ± 0.00250.146 ± 0.00200.159 ± 0.00150.161 ± 0.00010.229 ± 0.00300.250 ± 0.00100.292 ± 0.0020

-+-+-+-++++

75

24487296

120144168

0.032 ± 0.00070.069 ± 0.00100.081 ± 0.00150.089 ± 0.00070.151 ± 0.00200.153 ± 0.00300.167 ± 0.0025

----

-+-+-+

100

24487296

120144168

0.014 ± 0.00200.064 ± 0.00100.074 ± 0.00200.088 ± 0.00150.104 ± 0.00100.118 ± 0.00200.131 ± 0.0020

----

-+-+-+

125

24487296

120144168

0.008 ± 0.00100.048 ± 0.00200.063 ± 0.00150.072 ± 0.00200.080 ± 0.00070.098 ± 0.00100.120 ± 0.0015

------

-+AgNO3without CFE 24 - 168 0.050 ± 0.0020 -CFE Only 24 - 168 0.009 ± 0.0010 - -

Table 1: UV-VIS Measurement of Biosynthesized Silver Nanoparticles. Keys: OD: Optical Density; CFE: Cell Free Extract; AgNO3: Silver Nitrate; - -: Very Clear; -:= Light Sky Blue;

-+: Faint Brown; +: Light Brown; ++: Brown; +++: Dark Brown.

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Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

Figure 2: UV-Vis spectra of the cell free extract treated with 1 mM AgNO3 aqueous solution for 7 days.

Figure 3: SEM Image of the synthesized silver nanoparticles at x500 magnification.

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Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

Figure 4: X-Ray Diffraction Pattern of the Biosynthesized Silver Nanoparticles.

Table 2 shows the values for the X-ray Diffraction pattern as deduced from figure 4 and using the Debye-Scherrer equation, D= kλ/βcos θ to estimate the average size of the silver nanoparticles.

Peak Values (a.u) 2Ɵ (o) Ɵ (o) β (o) Height (cps) d-spacing (Å) D (nm)111 38.0 17.0 0.10 217.10 2.36 14.49200 44.4 22.20 0.15 43.40 2.04 9.98220 65.0 32.50 0.08 16.50 1.43 20.54311 77.5 38.75 0.09 28.30 1.22 19.28

Table 2: The Values of X-ray Diffraction Analysis of the Biosynthesized Silver Nanoparticles. Keys: a.u: Absorbance Units; o: Degree; β: Peak Width at Half Maximum Height; D: Nanoparticle Size; nm: Nanometer.

Using the Debye-Scherrer equation, “D” is the size of crystalline angle, “λ” is the X-ray wavelength (1.54 Å), “θ” is Bragg angle (10° ≤ 2 θ ≤ 80°), “K” is Scherer coefficient between 0.9-1, and “β” ½ is the maximum peak width by half of its height. The silver nanoparticle size is calculated for the four prominent peaks. Therefore, the average silver nanoparticle size using the Debye-Scherrer equation is, D ≈ 16.07 nm.

Figure 5 shows the FT-IR spectrum of the biosynthesized AgNPs revealing notable peaks at 3332.2, 2903.6, 1636.3, 1367.9, and 1162.3 cm-1.

98

Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

Figure 5: Fourier Transform0Infrared (FT-IR).

From the table 3, it was seen that the biosynthesized silver nanoparticles was stable over a period of 90 days as shown by the non-change in colour after 10 days of synthesis. This observation appears to agree with the near constant optical density and pH readings. The values were not statistically significant (p ≥ 0.05).

DiscussionThe biosynthesis of silver nanoparticles (Table 1) shows the gradual change in colour of the solution of cell free extract and silver

nitrate (AgNO3), which signify the synthesis of silver nanoparticles as the number of hours increased and in turn corresponds to increase in absorbance readings. It was seen that the concentration containing Cell-Free-Extract with 1mM AgNO3 in the ratios 1:25 (1 ml of fun-gal filtrate with 25 mL of 1 mM AgNO3) synthesized the silver nanoparticles better than the other ratios with the highest optical density measurement being 0.725 ± 0.0015 and a dark brown colour. It also showed that the controls, AgNO3 solution alone and cell free extract alone (0.050 ± 0.0020 and 0.009 ± 0.0010 respectively), relatively had the same optical density readings for the entire 168 hours and was also visibly observed by the non-change of colour over the same period. This is in accordance with the findings of Saklani., et al. [3] who synthesized silver nanoparticles using Escherichia coli and noticed colour change from fine yellow to reddish brown with time.

The addition of cell free extract to the silver nitrate solution resulted in the colour change of the solution from sky blue to reddish brown, which showed an observed absorption peak at 429.00 nm (Figure 2) assigned to surface plasmon resonance band of silver nanoparticles indicating its extracellular synthesis. The UV-Vis spectra showed no evidence of absorption in the spectral window 400-800nm for the cell free extract without silver nitrate, which was the control. This compares favourably with the results of Tsibakhashvili., et al. [17] who syn-thesized silver nanoparticles using Spirulina platensis and Streptomyces spp. with the UV-Vis analysis showing observed peak at 425 nm.

The scanning electron microscopy (SEM) image of the synthesized silver nanoparticles after 168 hours of reaction between the cell free extract and silver nitrate are shown in figure 3 at x500 magnification, which indicated the oval shape of the silver nanoparticles. Fur-

99

Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

Concentration (µg/ml) Time (days) O.D AT 550 nm Colour change pH

25

1

10 - 30

30 - 50

50 - 70

70 - 90

0.138 ± 0.0007

0.725 ± 0.0015

0.727 ± 0.0020

0.728 ± 0.0020

0.728 ± 0.0020

-+

+++

+++

+++

+++

5.2 ± 0.10

4.9 ± 0.20

4.6 ± 0.10

4.6 ± 0.10

4.6 ± 0.10

50

1

10 - 30

30 - 50

50 - 70

70 - 90

0.118 ± 0.0025

0.292 ± 0.0020

0.293 ± 0.0015

0.297 ± 0.0025

0.297 ± 0.0025

-+

+

+

+

+

5.4 ± 0.15

5.1 ± 0.10

5.1 ± 0.10

5.1 ± 0.10

5.1 ± 0.10

75

1

10 - 30

30 - 50

50 - 70

70 - 90

0.032 ± 0.0007

0.167 ± 0.0025

0.169 ± 0.0010

0.170 ± 0.0015

0.170 ± 0.0015

-

-+

-+

-+

-+

5.5 ± 0.20

5.3 ± 0.10

5.3 ± 0.10

5.3 ± 0.10

5.3 ± 0.10

100

1

10 - 30

30 - 50

50 - 70

70 - 90

0.014 ± 0.0020

0.131 ± 0.0007

0.135 ± 0.0010

0.137 ± 0.0015

0.137 ± 0.0015

-

-+

-+

-+

-+

5.7 ± 0.20

5.4 ± 0.10

5.4 ± 0.10

5.4 ± 0.10

5.4 ± 0.10

125

1

10 - 30

30 - 50

50 - 70

70 - 90

0.008 ± 0.0010

0.120 ± 0.0015

0.120 ± 0.0015

0.122 ± 0.0020

0.122 ± 0.0020

-

-+

-+

-+

-+

5.9 ± 0.10

5.6 ± 0.10

5.6 ± 0.10

5.6 ± 0.10

5.6 ± 0.10AgNO3without CFE 1 - 90 0.050 ± 0.0020 - 6.2 ± 0.10CFE Only 1 - 90 0.009 ± 0.0010 - - 6.9 ± 0.20

Table 3: Stability testing of biosynthesized AgNPs over a period of 90 days. Keys: OD: Optical Density; CFE: Cell Free Extract; AgNO3: Silver Nitrate; - -: Very Clear; -: Light Sky Blue;

-+: Faint Brown; +: Light Brown; ++: Brown; +++: Dark Brown.

ther experiment to determine the size was done by X-ray diffraction (Figure 4), which showed the XRD pattern of the synthesized silver nanoparticles with four prominent peaks found at 2Ɵ = 38.0°, 44.5°, 65.0° and 77.5°, which corresponds to (111), (200), (220), and (311) reflection planes of a face center cubic (FCC) structure of silver. The average size of the nanoparticle was determined (Table 2) using the Debye-Scherrer equation and it was found to be ≈ 16.07 nm, which compares favourably with the findings of Patil [16] whose work on the synthesis and characterization of silver nanoparticles using fungi and its antimicrobial activity reported the estimated average size of 12.5 nm.

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Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

The result of the Fourier transform-infrared (FT-IR) spectrum of the synthesized silver nanoparticles revealed notable peaks at 3332.2, 2903.6, 2105.9, 1636.3, 1427.6, 1367.9, 1315.8, 1162.3, 1107.0, 1051.1 and 894.6 cm-1 (Figure 5). The band at 3332.2 cm-1 almost cor-responds to O-H stretching H-bonded alcohols and phenols. The peak at 2903.6 cm-1 corresponds to O-H stretch carboxylic acids. The high intense peak at 1636.3 cm-1 corresponds to the bending vibration of N-H bonding vibrations of amines. The peak at 1367.9 cm-1 cor-responds to C-N stretching vibrations of aromatic amine group, while the band at 1162.3 cm-1 corresponds to C-N stretching alcohol. This indicates the presence and binding of proteins with silver nanoparticles, which can lead to their possible stabilization. This also agrees with the findings of Patil [16] who reported the FT-IR spectrum of synthesized silver nanoparticles showing peaks at 3410, 2934, 1748, 2624, 1371 and 1163 cm-1.

The synthesized silver nanoparticles was seen to be stable over a long period of time (90 days for the purpose of this study as shown in table 3). It was observed that there was gradual change in colour from day 1 to day 10 (sky blue to dark brown) as reflected by the increase in optical density readings from 0.138 ± 0.0007 to 0.725 ± 0.0015 with an average pH value of 5.2 ± 0.10 for the cell free extract to silver nitrate ratio of 1:25. The colour and pH remained approximately the same from day 10 to day 90 (O.D of 0.728 ± 0.0020 and pH of 4.6± 0.10). The same trend was observed in other ration concentrations. The change in colour and pH within the first ten days and the subsequent stability can be attributed to the dissociation constant of functional groups of the proteins that have binded with the silver nanoparticles. These results are in agreement with previously study of Pimprikar [18]. This may be because various biomolecules are involved in biological synthesis of silver nanoparticles. These molecules are likely to be inactive under extremely acidic conditions.

Statistical analysis showed that there was a significant difference in the synthesis of the silver nanoparticles at different fungal filtrate to silver nitrate ratios (p < 0.05), which meant that the more the interaction between the fungal filtrate and silver nitrate, the more the synthesis and the smaller the size of the silver nanoparticle synthesized. This could also be due to more binding to bioactive molecules as observed in this study.

Conclusion The results obtained in this present study support the use of biological sources such as Saccharomyces cerevisiae in the synthesis of

silver nanoparticles. The results further suggest that the silver nanoparticles are bonded to biomolecules such as amines, alcohols, car-boxylic acids and phenols. The binding with biomolecules may also account for the stability of silver nanoparticles over a long period of time. Biosynthesis of silver nanoparticles is therefore safe and ecofriendly. This study provides some scientific basis of the use of biological sources as cheap, safe and efficient means of synthesis.

AcknowledgementMy heartfelt gratitude goes to Dr. B. C. Akin-Osanaiye, my supervisor for her utmost understanding and guidance. I am extremely

grateful for everything especially the quality advice you gave me always from your wealth of experience, I sincerely desire that you never lack any good thing in your life, God bless you. I am also grateful to the Head of Department, all the lecturers and staff of the Department of Microbiology, University of Abuja, Gwagwalada, Abuja, Nigeria, for contributing immensely to my future. Your sacrifice and dedica-tion to service for humanity will win you glory in high places. I appreciate the efforts of the staff of Multi-User Laboratory, Ahmadu Bello University, Zaria, Nigeria, who assisted in characterizing the silver nanoparticles, the staff of Nanotech Research Group, Ladoke Akintola University, Ogbomoso, Nigeria, who provided standard silver nanoparticles for comparison.

Bibliography

1. Deepak V., et al. “An Insight into the Bacterial Biogenesis of Silver Nanoparticles, Industrial Production and Scale-up”. Metal Nanopar-ticles in Microbiology 1 (2011): 17-35.

2. Chatterjee S., et al. “Effect of Iron Oxide and Gold Nanoparticles on Bacterial Growth Leading towards Biological Application”. Journal of Nanobiotechnology 9 (2011): 34-35.

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Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae

Citation: OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye. “Biosynthesis of Silver Nanoparticles Using Baker’s Yeast, Saccharomyces cerevisiae”. EC Microbiology 15.12 (2019): 91-101.

3. Saklani V., et al. “Microbial Synthesis of Silver Nanoparticles: A Review”. Journal of Biotechnology and Biomaterials 13 (2012): 7.

4. Khatami M., et al. “Synthesis of Silver Nanoparticles using Seed Exudates of Sinapis arvensis as a Novel Bioresource, and Evaluation of their Antifungal Activity”. Bioresources and Bioprocessing 2 (2015): 19.

5. Song KC., et al. “Preparation of Colloidal Silver Nanoparticles by Chemical Reduction Method”. Korean Journal of Chemical Engineering 26.1 (2009): 153-155.

6. Lee AT., et al. “Synthesis of Oleic Acid-stabilized Silver Nanoparticles and Analysis of their Antibacterial Activity”. Material and Science Engineering 30.6 (2010): 910-916.

7. Ghosh S., et al. “Gnidiaglauca Flower Extract Mediated Synthesis of Gold Nanoparticles and Evaluation of its Chemocatalytic Potential”. Journal of Nanobiotechnology 10 (2012): 17.

8. Sriram MI., et al. “Biosynthesis of Silver and Gold nanoparticles using Bacillus licheniformis”. Methods in Molecular Biology 906 (2012): 33-43.

9. Gade A., et al. “Mycogenic Metal Nanoparticles: Progress and Applications”. Biotechnology Letters 32.5 (2010): 593-600.

10. Li X., et al. “Biosynthesis of Nanoparticles by Microorganisms and Their Applications”. Journal of Nanomaterials (2011): 270974.

11. Oskay M., et al. “Antibacterial Activity of some Actinomycetes Isolated from Farming Soils of Turkey”. African Journal of Microbiology Research 3.9 (2004): 441-446.

12. Kang K., et al. “Vascular Tube Formation and Angiogenesis Induced by polyvinylpyrrolidone-coated Silver Nanoparticles”. Toxicology Letters 205.3 (2011): 227-234.

13. Soltani-Nejad M., et al. “Extracellular Synthesis Gold Nanotriangles using Biomass of Streptomyces microflavus”. IET Nanobiotechnol-ogy 10.1 (2016): 33-38.

14. Khatami M., et al. “Antimicrobial Effect of Silver Nanoparticles Synthesized using Weed Seed Exudates against the Standard Strains of Bacillus cereus and Acinetobacter baumannii”. Journal of Microbial World 8.1 (2016): 18-25.

15. Akhlaghi H. “Green Synthesis of Silver Nanoparticles Using Pimpinella anisum L. Seed Aqueous Extract and Its Antioxidant Activity”. Journal of Chemical Health Risks 5.4 (2015): 257-265.

16. Patil SS., et al. “Nanoparticles. Synthesis and Reactivity in Inorganic”. Metal-Organic and Nano-Metal Chemistry 39 (2015): 65.

17. Tsibakhashvili N., et al. “Synthesis of Silver Nanoparticles using Bacteria”. Nano Studies 2 (2010): 179-182.

18. Pimprikar PS., et al. “Influence of Biomass and Gold Salt Concentration on Nanoparticle Synthesis by the Tropical Marine Yeast, Yar-rowia lipolytica NCIM 3589”. Colloids Surfaces B: Biointerfaces 74.1 (2009): 309-316.

Volume 15 Issue 12 December 2019©All rights reserved by OlobayotanIfeyomi Wilfred and Bukola Catherine Akin-Osanaiye.