HighlightsCrude glycerol is a byproduct of biodiesel industry.Crude glycerol is a valuable source for different valuable industrial products.Bioconversion of glycerol is a sustainable approach.This makes revenue to biodiesel industries and to overall economy of the biodiesel process.

Microalgae are important renewable feedstock to produce biodiesel and high‐value chemicals. Different wavelengths of light influence the growth and metabolic activities of algae. Recent research has identified the light‐sensing proteins called photoreceptors that respond to blue or red light. Structural elucidations of algal photoreceptors have gained momentum over recent years. These include channelrhodopsins, PHOT proteins, animal‐like cryptochromes, and blue‐light sensors utilizing flavin‐adenine dinucleotide proteins. Pulsing light has also been investigated as a means to optimize energy inputs into bioreactors. This study summarizes the current structural and functional basis of photoreceptor modulation to optimize the growth, production of carotenoids and other high‐value metabolites from microalgae. The review also encompasses novel photobioreactor designs that implement different light regimes including light wavelengths and time to optimize algal growth and desired metabolite profiles for high‐value products.

Background: Carotenoids and chlorophylls are important pigments as they have antioxidant properties and some such as lutein, astaxanthin and β-carotene are used as nutraceuticals. Pigment profiles are also used as taxonomic markers for phytoplankton. There are many solvent compositions published for the extraction of phytoplankton pigments. Here we report the testing of five different commonly used solvents and compare the overall pigment and lipid profiles and abundances using liquid chromatography-mass spectrometry (LC-MS) for three microalgal species with different pigment profiles.Results: A fast and sensitive LC-MS method was developed using a C18 column with a gradient consisting of isopropanol, acetonitrile and water. A total of 18 pigments along with phosphatidylcholines (PCs), triacylglycerols (TAGs) were separated in 25 mins. An extraction solvent composition of 90% acetone provided the broadest-coverage of pigments and lipids, while ethanol/hexane resulted in the highest extraction efficiency for chlorophyll and the non-polar triacylglycerol lipids. Overall, the result for the different mixtures shows the significant impact that solvent polarity has on the overall pigment and lipid profile and that no single mixture was optimal for all targets. Complete cell lysis using mechanical disruption such as bead beating is also an important step for quantitative extraction as chemical extraction on its own does not provide reproducible results.Conclusion: A 90% acetone extraction solvent mixture provides the broadest extraction of pigments from the species Haematococcus pluvialis, Desmodesmus subspicatus and Chlorella variabilis when coupled with bead beating. This extraction solvent is comparatively safe, polar and less toxic than other solvents. It was also found that none of the common solvent mixtures tested here provided the highest extraction efficiencies across all compound groups