Sustainable biodiesel production from oleaginous yeasts utilizing hydrolysates of various non-edible lignocellulosic biomasses

Biodiesel, as one of the best alternative fuels, has a number of advantages over petro diesel, such as originating from a renewable and domestic feedstock which reduces the net production cost of biodiesel. In the recent years, biodiesel has received increasing interest due to energy crisis worldwide along with exhausting reserves and the shortage of oil supplies. The major problem behind the use of vegetable oil for biodiesel production is sustainability because it directly competes with human food. To combat this problem, the other renewable sources have been developed as microbial oils have similarity to vegetable oils and extensively used for biodiesel production. Oleaginous yeasts have recently been suggested as microscopic biofactories and alternative lipid producer to vegetable oil for a more sustainable biodiesel industry. It is a potential novel technology where non-edible lignocellulosic biomasses are exploited as raw materials for biodiesel production from oleaginous yeasts which drop net greenhouse gas emissions by substituting the practice of fossil fuels and would convey benefits to rural economies and national energy security. The usage of oleaginous yeasts have many advantages over other renewable sources like faster growth rate, shorter life cycle, easier scale-up, with no effects from the season and climate variation, and can serve as the excellent oil accumulating renewable feedstocks which are non-competitive to food resources and do not require arable land. Non-edible lignocellulosic biomass, consists of three different types of natural polymers, namely cellulose, hemicellulose, and lignin, is the most abundant renewable bioresource in the biosphere. The production of fermentable sugars from hydrolysates of various non-edible lignocellulosic biomass, either by physical, chemical or enzymatic hydrolysis has been utilized as feedstock in bioethanol or biodiesel production, extensively. During hydrolysis generation of non-carbohydrate compounds, such as 5- hydroxymethylfurfural (HMF), furfural acetic acid and phenolic compounds have various effects on the growth of microorganisms, their metabolism, as well as on final products, presenting a key challenge in the biological conversion of biomasses.