The sample collected from an exponentially growing culture was diluted to 5 mg L1 of CHL and illuminated by red light-emitting diode (LED) lights with variable intensity. The resultant OER was measured with an oxygen sensor (OE-8250M, DKK-TOA, Japan) with a current transmitted across a 10 kU resistor and read on a digital multimeter (AD7461A, Advantest, Japan) (20).