Microalgae have been widely explored because of the diverse number of their worthwhile applications and potential as a source biomass for the production of biofuels and value-added materials. However, downstream techniques have yet to be fully developed to overcome techno-economic barriers. Flocculation is a superior method for harvesting microalgae from growth medium because of its harvesting efficiency, economic feasibility. Various kind of bio-flocculation harvesting methods are consider as attractive low cost and environmentally friendly options and able to harvest >90% biomass. Lipid recovery from microalgal cells is a major barrier for the biofuel industry because of process complexity and algae cell structure. Thus, the pretreatment method is necessary to disrupt the cell walls of microalgae and enhance lipid extraction. Many techniques, including dry methods of extraction, are already being implemented but found out that they are not efficient and cost-effective. Various new wet harvesting strategies have been claimed to extract major lipids in cost-efficient (30% less than conventional) way as wet technologies can eliminate the cost of cell drying and associated instruments. It is necessary to develop new methods which are energy and cost-effective, and environmentally friendlier for the commercialization of biofuels. Therefore, this review presents the advances in the progress of various flocculation harvesting methods with special emphasis on innovative bio-flocculation, the underlying mechanism of microalgae and flocculation. In this study also summarize the recent progress on microalgal oil extraction processes, and comparison was made between the processes in terms of sustainability, technology readiness, and applications in larger scales.

由于微藻的各种有价值的应用以及作为生产生物燃料和增值材料的来源生物质的潜力，因此已对微藻进行了广泛的研究。然而，下游技术尚未完全开发出来以克服技术经济障碍。絮凝是一种从生长培养基中收获微藻的优越方法，因为它的收获效率高，经济上可行。各种生物絮凝收获方法被认为是有吸引力的低成本和环境友好的选择，并且能够收获> 90％的生物量。由于工艺复杂性和藻类细胞结构，从微藻类细胞中回收脂质是生物燃料工业的主要障碍。因此，预处理方法对于破坏微藻的细胞壁并增强脂质提取是必要的。很多技巧 包括干法提取在内的方法已经在实施，但发现它们不高效且不具成本效益。由于湿法技术可以消除细胞干燥和相关仪器的成本，因此已声称有各种新的湿法收获策略可以经济高效地提取主要脂质（比传统方法少30％）。为了生物燃料的商业化，有必要开发新的方法，该方法既节能又经济，并且对环境友好。因此，本综述介绍了各种絮凝收获方法的进展，特别是创新的生物絮凝，微藻和絮凝的潜在机理。在这项研究中，还总结了微藻油提取工艺的最新进展，