Researchers at the University of Manchester say they have made a breakthrough in the development of synthetic pathways that will allow the renewable biosynthesis of propane. This discovery brings scientists closer to developing renewable propane.

The University of Manchester scientists say propane has good physiochemical properties that allow it to be stored and transported in a compressed liquid form. Under ambient conditions, propane serves as a clean-burning gas, which makes it an attractive target to become a renewable alternative to petroleum.

While natural metabolic pathways for the renewable biosynthesis of propane do not exist, scientists at the University of Manchester developed an alternative microbial biosynthetic pathway to produce renewable propane. The University of Manchester team modified existing fermentative butanol pathways using an engineered enzyme variant to redirect the microbial pathway to produce propane as opposed to butanol. The team was able to achieve propane biosynthesis, creating a platform for next-generation microbial propane production.

A microbial platform for renewable propane synthesis based on a fermentative butanol pathway

 

 

Propane, a major component of autogas or liquefied petroleum gas (LPG), is an emerging fuel for future energy supply and transportation [1]. Propane is the third most widely used motor fuel and about 20 million tonnes of propane gas are used per year to fuel motor vehicles [2]. It is estimated that propane provides heat and energy for more than 14 million homes worldwide annually [3],[4]. Propane also has an existing global market for a wide number of other stationary and mobile applications, such as low emission vehicles, gas burners and refrigeration systems [5]. Easy separation from liquid biotechnological processes as a gas and less energy requirements for liquefaction and storage offers potential advantages to propane over other gaseous fuels [6].

Natural metabolic pathways for the renewable biosynthesis of propane do not exist. The discovery of an aldehyde deformylating oxygenase (ADO) from cyanobacteria, however, has paved the way for synthetic alkane pathways to be constructed [7]-[9]. A microbial platform for propane generation dependent on fatty acid biosynthesis was recently reported [10]. The authors concluded that the pathway was limited by total flux through fatty acid synthesis (FAS). The most obvious example of this limitation comes from the markedly enhanced rate of propane synthesis observed when fatty acids were supplied to the external media. In the present study, we sought to bypass this limitation by generating new synthetic pathways that are not dependent on FAS. In this study, we designed a series of modified butyraldehyde pathways based on the CoA-dependent butanol pathways commonly found in Clostridium spp. Propane biosynthesis was thereafter achieved by interrupting the route to alcohol by the addition of ADO (Figure 1).