Assuaging Microalgal Harvesting Woes via Attached Growth: A Critical Review to Produce Sustainable Microalgal Feedstock

Abstract

Third-generation biofuels that are derived from microalgal biomass have gained momentum as a way forward in the sustainable production of biodiesel. Such efforts are propelled by the intention to reduce our dependence on fossil fuels as the primary source of energy. Accordingly, growing microalgal biomass in the form of suspended cultivation has been a conventional technique for the past few decades. To overcome the inevitable harvesting shortcomings arising from the excessive energy and time needed to separate the planktonic microalgal cells from water medium, researchers have started to explore attached microalgal cultivation systems. This cultivation mode permits the ease of harvesting mature microalgal biomass, circumventing the need to employ complex harvesting techniques to single out the cells, and is economically attractive. However, the main bottleneck associated with attached microalgal growth is low biomass production due to the difficulties the microalgal cells have in forming attachment and populating thereafter. In this regard, the current review encompasses the novel techniques adopted to promote attached microalgal growth. The physicochemical effects such as the pH of the culture medium, hydrophobicity, as well as the substratum surface properties and abiotic factors that can determine the fate of exponential growth of attached microalgal cells, are critically reviewed. This review aims to unveil the benefits of an attached microalgal cultivation system as a promising harvesting technique to produce sustainable biodiesel for lasting applications.

Application of microbial resources in biorefineries: Current trend and future prospects

“…The feedstock, substrate or media required to harbor such large and diverse amount of microbes can be availed through vastly available and negatively assessed waste, a value generating feedstock. Such biorefineries have attracted attention of the researchers as the microbes offer biomass cultivation on a non-agricultural land, climate and time independent cultivation, short harvesting cycle, less environmental load and complete biodegradable nature [ [3] , [4] , [5] ]. Moreover, microbial biorefinery put forward a holistic model for economic, environmental and social growth by sequestering carbon from renewable carbons sources such as environment (in case of autotrophic microbes), lignocellulosic waste, industrial waste and municipal waste as described in Fig.…”

Integrated electrocoagulation-flotation of microalgae to produce Mg-laden microalgal biochar for seeding struvite crystallization

“…These advantages can be exploited for seeding struvite crystallization to minimize the induction time and enhance phosphate recovery and crystal size. However, due to the small cell size, low cell concentration and culture density of microalgae as equal to water, the cost and energy associated with harvesting microalgae makes their utilization uneconomical 41 , 42 . Among the existing harvesting techniques, coagulation, flocculation, filtration, and centrifugation are found to be more appropriate for practical applications.…”