Effects of Cultural Conditions in Enhancing the Production of Anti-MRSA Activity of Lasiodiplodia pseudotheobromae IBRL OS-64, an Endophytic Fungus Isolated from Leaf of Ocimum sanctum L. in Submerged Fermentation System

Biocontrol Screening of Endophytes: Applications and Limitations

The considerable loss of crop productivity each year due to plant disease or pathogen invasion during pre- or post-harvest storage conditions is one of the most severe challenges to achieving the goals of food security for the rising global population. Although chemical pesticides severally affect the food quality and health of consumers, a large population relies on them for plant disease management. But currently, endophytes have been considered one of the most suitable biocontrol agents due to better colonization and acclimatization potential. However, a very limited number of endophytes have been used commercially as biocontrol agents. Isolation of endophytes and their screening to represent potential characteristics as biocontrol agents are considered challenging by different procedures. Through a web search using the keywords "endophytes as biocontrol agents" or "biocontrol mechanism of endophytes," we have succinctly summarised the isolation strategies and different in vitro and in vivo biocontrol screening methods of endophytic biocontrol agents in the present review. In this paper, biocontrol mechanisms of endophytes and their potential application in plant disease management have also been discussed. Furthermore, the registration and regulatory mechanism of the endophytic biocontrol agents are also covered.

Effect of Culture Medium Incorporated with Ocimum sanctum Extract in Enhancing Anti-MRSA activity of Endophytic Fungus, Lasiodiplodia pseudotheobromae

The effect of incorporating plant extract in the culture medium on anti-MRSA activity of Lasiodiplodia pseudotheobromae IBRL OS-64, was investigated in the present study. On disk diffusion assay, the ethyl acetate fungal extract from culture medium supplemented with host plant extract (HPE) of Ocimum sanctum leaves demonstrated good anti-MRSA activity with a diameter inhibition zone of 22.6±0.6 mm. Meanwhile, the minimal inhibition concentration (MIC) values of the extract from YES broth and YES broth incorporated with HPE were 1000 µg/mL and 250 µg/mL, respectively. The MBC values were 8000 µg/mL and 500 µg/mL, respectively. The YES + HPE extracts exerted bactericidal effect against the test bacteria since the MBC/MIC ratio was less than or equal to 4. The time-kill study revealed a 90% of growth reduction of MRSA ATCC 33591 after 16 h exposure to the fungal extract cultured in YES + HPE. Ironically, for fungal extract grown in YES broth, time-kill curve showed a regrowth pattern of bacterial cells after 24 h exposed to the extract. Therefore, the present study suggested that the addition of HPE in the culture medium could enhance the anti-MRSA activity of endophytic fungus, L. pseudotheobromae IBRL OS-64 against MRSA ATCC 33591.