I'm working on the behaviour of Fusarium oxysporium in fermenting fructose to ethanol and during daily analysis of fermenting culture the mycelial weight doubled followed by an increase in pH .. after 48 hours the mycelial weight decreased to 70%!! at max pH and ethanol production increased.. why?
Hi Ahmed
Can you explain more about your process? I knew that yeasts produce alcohol when the growth conditions are anaerobe.
Regarding the trend in the pH change, as microorganisms usually use carbon sources, they produce acidic products and so, the pH decreases and the time period can be different from one to another microorganism. Then because of production of alkali products the pH increases and later it can fix or lower again.
Good luck
Hi Dr. Ahmed
Did you stabilized the used fusarium inocula accurately in all of the tested pH values? Did you prepared triplicates of all treatments? If yes, the answer will be that the physiological processes in any living organisms are affected by pH of the medium. The biosynthesis pathways may be altered, where some enzymes are deactivated at the non-suitable pH values, which will be resulted in attenuated pathway products.
thank you all for those logic answers . but stil i have asked about the possibility of mycelial decrease in weight that might be related to early autolysis that took place due to altering in pH?
The growth must have increased during the log phase and it declined in the declining phase when there was no availability of the substrate. During decline period lysis of the mycelia takes place in the absence of substrate and thus increase of pH. Some alcohol could have liberated from the lysed mycelia. The reduction in weight of mycelia may be the result of lysis in decline phase.
You can repeat the experiment to confirm these facts even with variable amount of substrate.
How do you measure mycelial weight?
What are the carbon and nitrogen sources and their concentration in the medium?
As you mentioned, autolysis can be the cause! It occurs mostly at the end of stationary phase for bacteria and the OD and weigh decrease. There may be similar problem with your experiments.
Good luck
Jai precisely explained the cause of reduction in mycial mass. Sporulation, a natural process of fungal life cycle, starts due to carbon depletion or any other changes in the cultural environment that do not support mycelial growth anymore. You may confirm it by checking for abundance of spores in the culture broth under a microscope. Good luck.
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