Abstract
Volatile Fatty Acids (VFA) are small organic compounds that have attracted much attention lately, due to their use as a carbon source for microorganisms involved in the production of bioactive compounds, biodegradable materials and energy. Low cost production of VFA from different types of waste streams can occur via dark fermentation, offering a promising approach for the production of biofuels and biochemicals with simultaneous reduction of waste volume. VFA can be subsequently utilized in fermentation processes and efficiently transformed into bioactive compounds that can be used in the food and nutraceutical industry for the development of functional foods with scientifically sustained claims. Microalgae are oleaginous microorganisms that are able to grow in heterotrophic cultures supported by VFA as a carbon source and accumulate high amounts of valuable products, such as omega-3 fatty acids and exopolysaccharides. This article reviews the different types of waste streams in concert with their potential to produce VFA, the possible factors that affect the VFA production process and the utilization of the resulting VFA in microalgae fermentation processes. The biology of VFA utilization, the potential products and the downstream processes are discussed in detail.
Highlights
The term Volatile Fatty Acids (VFA) is applied to short-chain fatty acids, usually consisted of two to six carbon atoms, such as acetic, butyric or propionic acid [1]
Fermentation 2017, 3, 54 transformation into value-added products. Bioactive compounds such as omega-3 fatty acids can be obtained through fermentation processes that use VFA as carbon source for microorganisms
According to European Food Safety Authority (EFSA-Q-2004-107), there are two main categories of omega-3 fatty acids (n-3 polyunsaturated fatty acids, PUFAs), which differ in function and requirements; the first refers to α-linolenic acid (ALA) produced from vegetable oil, while the other includes long chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) from marine sources
Summary
The term Volatile Fatty Acids (VFA) is applied to short-chain fatty acids, usually consisted of two to six carbon atoms, such as acetic, butyric or propionic acid [1]. Microalgae use short-chain fatty acids to produce metabolites, such as long chain unsaturated fatty acids (e.g., omega-3 fatty acids or arachidonic acid) or carotenoids In this case, the first step of breaking down the carbon sources to simple sugars is eliminated, since VFA provide microalgae with a carbon chain backbone ready to be elongated to polyunsaturated fatty acids (PUFAs) [4]. The first step of breaking down the carbon sources to simple sugars is eliminated, since VFA provide microalgae with a carbon chain backbone ready to be elongated to polyunsaturated fatty acids (PUFAs) [4] This ability of certain microalgal species is opening a new perspective in the industrial production of high added-value products, while using as raw material undesirable persistent pollutants. New sources (e.g., heterotrophic microalgae) and innovative production processes not relying on agricultural area and food grade carbon sources are needed to supply this gap
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