A state of the art review on the co-cultivation of microalgae-fungi in wastewater for biofuel production.

The microalgae have a great potential as the fourth generation biofuel feedstock to deal with energy crisis, but the cost of production and biomass harvest are the major hurdles in terms of large scale production and applications. Using filamentous fungi to culture targeted alga for biomass accumulation and eventually harvesting is a sustainable way to mitigate environmental impacts. Microalgal co-culture method could be an alternative to overcome limitations and increase biomass yield and lipid accumulation. It was found to be the high feasibility for the production of biofuels from fungi and microalgae using wastewater. This article aimed to state the synergistic approaches, their culture protocols, harvesting procedure and their potential biotechnological applications. Additionally, algal-fungal consortia could digest cellulosic biomass, potentially reducing operating costs as part of industrial need. As a result of co-cultivation, biofuel production could be economically feasible owing to its excellent ability to treat wastewater and be eco-friendly. The implications of the innovative co-cultivation technology have demonstrated the potential for further development based on the policies that have been supported and implemented.

Valorization of wastewater: A paradigm shift towards circular bioeconomy and sustainability.

Limitation in the availability of natural resources like water is the main drive for focussing on resource recovery from wastewater. Rapid urbanization with increased consumption of natural resources has severely affected its management and security. The application of biotechnological processes offers a feasible approach to concentrating and transforming wastewater for resource recovery and a step towards a circular economy. Wastewater generally contains high organic materials, nutrients, metals and chemicals, which have economic value. Hence, its management can be a valuable resource through the implementation of a paradigm transformation for value-added product recovery. This review focuses on the circular economy of "close loop" process by wastewater reuse and energy recovery identifying the emerging technologies for recovering resources across the wastewater treatment phase. Conventional wastewater treatment technologies have been discussed along with the advanced treatment technologies such as algal treatment, anammox technology, microbial fuel cells (MFC). Apart from recovering energy in the form of biogas and biohydrogen, second and third-generation biofuels as well as biohythane and electricity generation have been deliberated. Other options for resource recovery are single-cell protein (SCP), biopolymers as well as recovery of metals and nutrients. The paper also highlights the applications of treated wastewater in agriculture, aquaponics, fisheries and algal cultivation. The concept of Partitions-release-recover (PRR) has been discussed for a better understanding of the filtration treatment coupled with anaerobic digestion. The review provides a critical evaluation on the importance of adopting a circular economy and their role in achieving sustainable development goals (SDGs). Thus, it is imperative that such initiatives towards resource recovery from wastewater through integration of concepts can aid in providing wastewater treatment system with resource efficiency.

Recent nanobiotechnological advancements in lignocellulosic biomass valorization: A review.

Increase in human population, rapid industrialization, excessive utilization of fossil fuel utilization and anthropogenic activities have caused serious threats to the environment in terms of greenhouse gas emissions (GHGs), global warming, air pollution, acid rain, etc. This destruction in sustainability can be averted by a paradigm shift in the fuel production from fossil resources to bioenergy. Amongst different forms of bioenergy, lignocellulosic biomass can be utilized as an attractive substrate for the production of several high-value products owing to its renewability, easy availability, and abundance. Additionally, utilization of these waste biomasses reduces the environmental hazards associated with its disposal. Impedance of lignin and crystalline nature of cellulose pose major bottlenecks in biomass based energy. Though, several physio-chemicals processes are recommended as mitigation route but none of them seems to be promising for large scale application. In recent years, a right fusion of biological treatment combined with nanotechnology for efficient pretreatment and subsequent hydrolysis of biomass by ubiquitous enzymes seems to be promising alternative. In addition, to overcome these difficulties, nanotechnology-based methods have been recently adopted in catalytic valorization of lignocellulosic biomass. The present review has critically discussed the application of nano-biotechnology in lignocellulosic biomass valorization in terms of pretreatment and hydrolysis. A detailed discussion on the application of various nanoparticles in these processes, enzyme immobilization and end-production utilization is presented in this review. Finally, the review emphasizes the major challenges of this process along with different routes and recommendations to address the issues.

A green and sustainable approach on statistical optimization of laccase mediated delignification of sugarcane tops for enhanced saccharification.

Bioethanol production from lignocellulosic biomass is a promising approach towards finding an alternative for transportation fuels that is driven by the prerequisite to lessen our dependency on fossil fuels, increase energy security and mitigate greenhouse gas emission. Recalcitrance of lignocellulosic biomass is a major hindrance in bioethanol production. Hence, an efficient pretreatment method is necessary for degradation of lignin and providing accessibility of holocellulose for hydrolysis. In an attempt to overcome this bottleneck, laccase mediated delignification of sugarcane tops was studied using central composite design (CCD) based on response surface methodology (RSM). The effect of different process parameters such as temperature, pH, solid loading, enzyme titre and incubation time were evaluated. It was observed that under optimum conditions of pH 7, solid loading of 21% (w/v), enzyme titre of 430.3 IU/mL, temperature of 40 °C and incubation of 6 h, maximum delignification of 79.1% was achieved. Compositional analysis, energy density measurement and water retention capacity of the biomass was also conducted along with GC-MS analysis for identification of low molecular compounds formed during delignification. Structural characterization of the biomass before and after pretreatment process were analysed by Scanning Electron Microscopy (SEM), Fourier-Transform Infra-Red Spectroscopy (FTIR) and X-Ray Diffraction Spectroscopy (XRD) that further substantiated the delignification of sugarcane tops.