Algal biorefinery culminating multiple value-added products: recent advances, emerging trends, opportunities, and challenges.

Algal biorefinery is rising as a prominent solution to economically fulfill the escalating global requirement for nutrition, feed, fuel, and medicines. In recent years, scientific productiveness associated with microalgae-based studies has elaborated in multiplied aspects, while translation to the commercial level continues to be missing. The present microalgal biorefinery has a challenge in long-term viability due to escalated market price of algal-mediated biofuels and bioproducts. Advancements are required in a few aspects like improvement in algae processing, energy investment, and cost analysis of microalgae biorefinery. Therefore, it is essential to recognize the modern work by understanding the knowledge gaps and hotspots driving business scale up. The microalgae biorefinery integrated with energy-based products, bioactive and green compounds, focusing on a circular bioeconomy, is urgently needed. A detailed investigation of techno-economic analysis (TEA) and life cycle assessment (LCA) is important to increase the market value of algal products. This review discusses the valorization of algal biomass for the value-added application that holds a sustainable approach and cost-competitive algal biorefinery. The current industries, policies, technology transfer trends, challenges, and future economic outlook are discussed. This study is an overview through scientometric investigation attempt to describe the research development contributing to this rising field.

Characterization of the Chloroplast Genome Facilitated the Transformation of Parachlorella kessleri-I, A Potential Marine Alga for Biofuel Production.

INTRODUCTION: The microalga Parachlorella kessleri-I produces high biomass and lipid content that could be suitable for producing economically viable biofuel at a commercial scale. Sequencing the complete chloroplast genome is crucial for the construction of a species-specific chloroplast transformation vector. METHODS: In this study, the complete chloroplast genome sequence (cpDNA) of P. kessleri-I was assembled; annotated and genetic transformation of the chloroplast was optimized. For the chloroplast transformation, we have tested two antibiotic resistance makers, aminoglycoside adenine transferase (aadA) gene and Sh-ble gene conferring resistance to spectinomycin and zeocin, respectively. Transgene integration and homoplasty determination were confirmed using PCR, Southern blot and Droplet Digital PCR. RESULTS: The chloroplast genome (109,642 bp) exhibited a quadripartite structure with two reverse repeat regions (IRA and IRB), a long single copy (LSC), and a small single copy (SSC) region. The genome encodes 116 genes, with 80 protein-coding genes, 32 tRNAs and 4 rRNAs. The cpDNA provided essential information like codons, UTRs and flank sequences for homologous recombination to make a species-specific vector that facilitated the transformation of P. kessleri-I chloroplast. The transgenic algal colonies were retrieved on a TAP medium containing 400 mg. L-1 spectinomycin, but no transgenic was recovered on the zeocin-supplemented medium. PCR and Southern blot analysis ascertained the transgene integration into the chloroplast genome, via homologous recombination. The chloroplast genome copy number in wildtype and transgenic P. kessleri-I was determined using Droplet Digital PCR. CONCLUSION: The optimization of stable chloroplast transformation in marine alga P. kessleri-I should open a gateway for directly engineering the strain for carbon concentration mechanisms to fix more CO2, improving the photosynthetic efficiency and reducing the overall biofuels production cost.

Life cycle assessment of Chlorella species producing biodiesel and remediating wastewater.

Constantly rising energy demands, finite fossil fuel reserves and deteriorating environmental conditions have invoked worldwide interest to explore the sustainable sources of renewable biofuels. Locally adapted photosynthetic oleaginous microalgae with rapid growth on variable temperatures could be an ideal way for bioremediating the wastewater (WW) while producing the feedstock for biodiesel. To test this notion, an unknown strain was isolated from a sewage fed lake (Neela-Hauz). It was discerned as Chlorella sorokiniana-I using the 16S rDNA and 18S rDNA barcodes. The culture conditions such as pH, illumination, different temperature ranges and growth medium were cohesively optimized prior to the assessment of C. sorokiniana-I's efficacy to remediate the WWand biodiesel production. The strain has thrived well up to 40°C when continuously grown for 15 days. The highest lipid accumulation and biomass productivity were recorded in 100% WW. Fatty acid methyl ester (FAME) content was observed to be more than twice in WW (47%), compared to control synthetic media, TAP (20%) and BG11 (10%), which indicate the importance of this new isolate for producing economically viable biodiesel. Moreover, it is highly efficient in removing the total nitrogen (77%), total phosphorous (81%), iron (67%) and calcium (42%) from the WW. The quality of WW was considerably improved by reducing the overall chemical oxygen demand (48%), biological oxygen demand (47%) and alkalinity (15%). Thus, C. sorokiniana-I could be an ideal alga for the tropical countries in the remediation of WW while producing feedstock for biodiesel in a cost-effective manner.