Antimicrobial Effects of Ocimum gratissimum Extracts on the Spoilage Organisms Isolated from Yoghurt Samples
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Date
2025-06-14
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UJMR
Abstract
Ocimum gratissimum (OG) is recognised for its nutritional, antioxidant, and antimicrobial
properties, making it a strong candidate for natural food preservation. This study evaluated
the effects of ethanolic and aqueous OG leaf extracts against spoilage organisms isolated
from laboratory-prepared yoghurt samples stored at room temperature for ten days. The
agar well diffusion technique was employed for antimicrobial screening, while the broth
microdilution method was used to determine both minimum inhibitory concentration (MIC)
and minimum cidal concentration (MCC). The isolated organisms included Bacillus subtilis,
Bacillus spp., Saccharomyces cerevisiae, Saccharomyces bulderi, Pichia kudriavzevii,
Aspergillus niger, and Aspergillus flavus, identified by standard microbiological methods.
The aqueous extract at a concentration as low as 62.50 mg/mL inhibited Bacillus subtilis,
Saccharomyces bulderi, Pichia kudriavzevii, and Saccharomyces cerevisiae, with inhibition
zones ranging from 5.00±0.27 to 6.20±0.87 mm. The ethanolic extract exhibited
antimicrobial effects against Bacillus subtilis, Bacillus spp., Saccharomyces bulderi, Pichia
kudriavzevii, and Saccharomyces cerevisiae at the same concentration (62.50 mg/mL), but
with larger inhibition zones ranging from 5.30±0.45 to 11.35±2.10 mm. The aqueous extract
showed substantial inhibition of Bacillus subtilis, Saccharomyces bulderi, and Pichia
kudriavzevii, with an MIC of 62.50 mg/mL. In contrast, the ethanolic extract demonstrated
an MIC of 31. 25 mg/mL for Bacillus subtilis, Bacillus spp., and Aspergillus niger. The MCC of
the aqueous extract was 250 mg/mL for Bacillus subtilis, Saccharomyces bulderi, Pichia
kudriavzevii, Aspergillus flavus, and Saccharomyces cerevisiae, while the MCC of the
ethanolic extract was 125 mg/mL for Bacillus subtilis and Bacillus spp. Overall, the OG
extracts exhibited substantial antimicrobial effects, effectively inhibiting the growth of
spoilage organisms isolated from stored yoghurt samples. Harnessing the potential of OG
can lead to an extended shelf life for yoghurt, positioning OG as a promising natural
preservative
Description
This research work is to assess the antimicrobial effects of the leaf extract of the plant Ocimum gratissimum on the Spoilage Organisms Isolated from Yoghurt Samples.
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