For efficient production of microbial lipids also known as single cell oil (SCO), selection of favorable growth conditions including the substrate for maximum conversion into storage lipids is imperative. Utilization of lignocellulosic biomass for microbial oil production is a promising approach as it is renewable, sustainable, and available in abundance, with a significant quantity of fermentable sugars. Because of their intricate structure and biomolecular composition, lignocellulosic substrates exhibit high recalcitrance and demand specific pretreatments to release the fermentable sugars. However, pretreating the lignocellulosic substrate not only produces assimilable sugars but also various fermentation inhibitors that can significantly impede microbial growth and/or lipogenesis. Therefore, in this review, we discuss different inhibitors present in the lignocellulosic hydrolysates, and the impact on oleaginous microbial growth and metabolic activity, particularly concerning lipid production. Furthermore, the mode of inhibition of the various inhibitors and potential strategies to detoxify these are discussed in this review.

The global fish industry is an essential contributor to food security and the economy; however, it produces considerable quantities of fish waste. Depending on species and processing methods, 20–80% of fish biomass is discarded as waste, amounting to almost 64 million tons annually. Conventional disposal methods such as landfilling, incineration, and wastewater discharge cause environmental pollution and greenhouse gas emissions. Therefore, for sustainable development, it is important to valorize fish waste into renewable energy and value-added products. Hence, this review aims to encourage the technical development of fish waste into bioenergy and bioresources by thoroughly studying key technologies for converting it into biogas, biodiesel, fertilizer, animal feed, and biochar. Although several studies have explored these technologies, most remain disjointed and lack a systematic assessment. Therefore, this work attempted to critically evaluate the technological principles, advantages, limitations, and optimization strategies of current valorization approaches. Furthermore, several recommendations have been proposed, including conducting pilot-scale trials, producing higher value-added products within a biorefinery system. Overall, this review provides a holistic outlook on the energy and resource conversion of fish waste, supporting sustainable waste management.