Akash Anandraj

Bioprospecting for hyper-lipid producing microalgal strains for sustainable biofuel production

Global petroleum reserves are shrinking at a fast pace, increasing the demand for alternate fuels. Microalgae have the ability to grow rapidly, and synthesize and accumulate large amounts (approximately 20-50% of dry weight) of neutral lipid stored in cytosolic lipid bodies. A successful and economically viable algae based biofuel industry mainly depends on the selection of appropriate algal strains. The main focus of bioprospecting for microalgae is to identify unique high lipid producing microalgae from different habitats. Indigenous species of microalgae with high lipid yields are especially valuable in the biofuel industry. Isolation, purification and identification of natural microalgal assemblages using conventional techniques is generally time consuming. However, the recent use of micromanipulation as a rapid isolating tool allows for a higher screening throughput. The appropriate media and growth conditions are also important for successful microalgal proliferation. Environmental parameters recorded at the sampling site are necessary to optimize in vitro growth. Identification of species generally requires a combination of morphological and genetic characterization. The selected microalgal strains are grown in upscale systems such as raceway ponds or photobireactors for biomass and lipid production. This paper reviews the recent methodologies adopted for site selection, sampling, strain selection and identification, optimization of cultural conditions for superior lipid yield for biofuel production. Energy generation routes of microalgal lipids and biomass are discussed in detail.

PAM fluorometry as a tool to assess microalgal nutrient stress and monitor cellular neutral lipids

This study investigated the use of Pulse Amplitude Modulated (PAM) fluorometry to measure nutrient induced physiological stress and subsequent synthesis of cellular neutral lipids. A freshwater Chlorella sp. was subjected to complete nutrient stress (distilled H2O) and selective nutrient stress in modified BG-11 media (BG-11-N, BG-11-P and BG-11-Fe). Physiological stress was recorded using parameters, rETR, Fv/Fm, Ek, α and NPQ. Induced stress became evident when these parameters were significantly altered, suggesting the onset of neutral lipid synthesis. Complete nutrient stress induced the highest yield of cellular neutral lipids (∼49%) compared to absence of selected nutrients (∼30%). Physiological stress was recorded by a significant decrease in rETR (75%), Fv/Fm (36%), and Ek (60%) and an increase in NPQ (83%). Optimization of neutral lipids occurred by initially maximizing the biomass and subsequently subjecting the harvested biomass to complete nutrient stress.

Robust photosystem I activity by Cyanothece sp. (Cyanobacteria) and its role in prolonged bloom persistence in lake St Lucia, South Africa

Worldwide, cyanobacterial blooms are becoming more frequent, exacerbated by eutrophication, anthropogenic effects, and global climate change. Environmental factors play a direct role in photosynthesis of cyanobacteria and subsequent cellular changes, growth, and bloom dynamics. This study investigated the photosynthetic functioning of a persistent bloom-forming (18xa0months) cyanobacterium, Cyanothece sp., isolated from Lake St Lucia, South Africa. DUAL-PAM fluorometric methods were used to observe physiological responses in Cyanothece sp. photosystems I and II. Results show that photosystem I activity was maintained under all environmental conditions tested, while photosystem II activity was not observed at all. Out of the environmental factors tested (temperature, salinity, and nitrogen presence), only temperature significantly influenced photosystem I activity. In particular, high temperature (40xa0°C) facilitated faster electron transport rates, while effects of salinity and nitrogen were variable. Cyanothece sp. has shown to sustain bloom status for long periods largely because of the essential role of photosystem I activity during highly dynamic and even extreme (e.g., salinities higher than 200) environmental conditions. This ensures the continual supply of cellular energy (e.g. ATP) to important processes such as nitrogen assimilation, which is essential for protein synthesis, cell growth and, therefore, bloom maintenance.

Photosystem I Fluorescence as a Physiological Indicator of Hydrogen Production in Chlamydomonas reinhardtii

This study investigated the interrelations between hydrogen synthesis and Photosystem I electron transport rate in Chlamydomonas reinhardtii. The fluorescence of both photosystems (PS I and PS II) was monitored using a Dual Pulse Amplitude Modulated (PAM) Fluorometer. Hydrogen synthesis was induced by eliminating sulphur from the growth media (TAP-S). Multiple physiological parameters [rETR, Y (I), Y (II), NPQ, α, Fv/Fm and YI:YII] were recorded using the Dual PAM and correlated to hydrogen produced. There was a 66% increase in Photosystem I rETRmax during hydrogen production. A significant direct correlation existed between PS 1 rETRmax and hydrogen evolution values over the ten-day period (ru202f=u202f0.895, pu202f<u202f0.01) indicating that PS I can be considered as a driver of H2 production. Significant correlations between rETRmax of PS I and H2 evolution suggest a novel physiological indicator to monitor H2 production during the three critical phases identified in this study.

Sustainable Biodiesel Production Using Wastewater Streams and Microalgae in South Africa

The diminishing petroleum reserves in the world call for sustainable use of cheaply and readily available substrates such as wastewater streams for biomass and lipid production by microalgae. Treated wastewater is rich in macronutrients, such as nitrates and phosphates, and can therefore be used as a substrate for microalgal cultivation in open raceway ponds. The chemistry and composition of treated wastewater is of significance since it is made up of a wide range of compounds that support microalgal growth. The use of raceway pond technology utilizing wastewater streams feed is a new phenomenon that provides much needed phytoremediation of the wastewater as well as facilitating microalgal mass production. Macronutrient utilization by the microalgae justifies the application of treated wastewater as a sustainable raw material for renewable bioenergy production. The operational parameters in the raceway pond such as light intensity, photoperiod, pH, nutrients, salinity, and temperature are carefully optimized for maximal biomass and lipid yield. The biomass and lipid produced using the raceway pond system undergoes downstream processing in order to get the final product. The lipids are converted via transesterification to produce algae biodiesel. Other biologically active compounds and novel phytochemicals can also be derived from microalgae.