No abstract

Baker's yeast, Saccharomyces cerevisiae, is reported as possessing the ability to convert glycerol to 1,3-propanediol. Various fermentation conditions were tested at different temperatures. Under anaerobic fermentation at 25 °C, 93.6 wt% glycerol was consumed, yielding 42.3 wt% 1,3-propanediol.

A solar reactor was designed to perform the conversion of starch to ethanol in a single step. An aqueous starch solution (5 wt %) was fed into the reactor bed charged with Baker's yeast (Saccharomyces cerevisiae) and amylase, resulting in approximately 2.5 wt % ethanol collected daily (ca. 25 mL day(-1) ). A significant amount of ethanol (38 g) was collected over 63 days, corresponding to 84 % of the theoretical yield. The production of ethanol without additional energy input highlights the significance of this new process. The ethanol produced was also demonstrated as a potential fuel for direct ethanol fuel cells. Additionally, the secondary metabolite glycerol was fully reduced to a value-added product 1,3-propanediol, which is the first example of a fungal strain (Baker's yeast) converting glycerol in situ to 1,3-propanediol.

A novel catalyst, SrO on microporous activated carbon (SrO/C), was synthesized by sonochemical deposition of SrO on carbon. The SrO/C demonstrated high catalytic performance in solar-heated transesterification reactions of canola oil, soybean oil, and waste cooking oil (WCO). The catalytic activity increased more than 5-fold (corresponding to 81% less catalyst compared to pristine SrO), using soybean oil as a feedstock. Similar enhancement was also observed with canola oil and WCO, where the catalytic activity improved more than 4-fold, corresponding to 76% less catalyst compared to pristine SrO. A yield of 98.5 wt % fatty acid methyl esters (FAME) was obtained from WCO in 60 min using a 1:6 oil:methanol molar ratio and 7.1 wt % SrO/C catalyst (24% SrO loading) at 46 °C (solar heating). The SrO/C catalyst was used for four consecutive transesterification reactions of WCO without any significant decrease in its catalytic activity (only 3% decrease in FAME yield and less than 5 ppm leaching). The results confirm the stability and sustained activity of the SrO/C catalyst, which is of great importance for industrial applications. The proposed method can significantly minimize the cost of biodiesel production by harnessing solar thermal energy. Performing the reaction without any additional energy consumption for heating, using a carbon-supported catalyst and low-cost feedstock, make the current biodiesel production a simple, economically worthwhile, environmentally-friendly, and industrially appealing process.