Industrial scale NAD synthesis
While light induction is a potentially viable means for the production of important molecules or constructs, such a process is only practical if the production can be achieved on an industrial scale. Similar reasoning is applied to biological production processes in general, which need to demonstrate economically sustainable, environmentally friendly, large-scale production capabilities in order to replace any existing non-biological processes. In order for light-inducible, biological production of NAD to be successful, we need to identify an appropriate system that optimises NAD synthesis on a suitably large scale at minimal cost.
Such a circuit may be controlled by the 555 integrated circuit (see below). The 555 packages up some useful components into a neat bundle and avoids having to assemble many separate parts. The 555 employs the use of two comparators (triangle shapes) and a flip-flip (rectangle). A comparator compares two voltages to give a digital output. Ideally, the comparator gives the output voltage 1 when the (+) voltage is greater than the (-) voltage and gives output 0 when (+)<(-). The comparator gives a method for measuring some threshold voltage level. The flip-flop is a type of switch with memory. When it receives voltage through the S (set), it provides a current to the Q output and will continue to do this even if the voltage to the S stops. If a current is then applied to the R (reset), the Q output will stop and stay this way even if the R voltage stops. This memory switch gives a method for opening and closing an external circuit using a small signal voltage.
Analogous to our present investigation is the development of biological production process for the production of H2. Achieved using any of four classes of bacteria or algae, this process has demonstrated significant advantages over other, non-biological processes, namely their ability to be conducted under ambient conditions without the use of harmful catalysts (Adessi and De Philippis 2014). However, while biological H2 production processes have been demonstrated as sustainable, renewable, and energy-efficient processes, achieving production on scales similar to non-biological processes remains a significant challenge.
The following circuit achieves the desired connections to between the pins of the 555 so that when the capacitor is low, the trigger and threshold are also low, causing the flip-flop to set and the Q output to go high. This simultaneously causes the output circuit to be driven, begins charging the capacitor and closes the discharge switch. Then there is a delay where nothing happens as the capacitor charges (time1). When the capacitor is charged the two comparators switch, causing the flip-flop to reset and the Q output to go low, cutting the external output circuit and opening the discharge switch. Then there is a second delay as the capacitor is discharging (time2). Then the capacitor has completely discharged, the comparators switch again and the process repeats. This circuit is known as astable as the cycle will repeat indefinitely.