The growing demand for biodegradable and biocompatible bioplastics has intensified interest in biopolymerbased materials such as polyhydroxyalkanoates (PHA) and polyhydroxybutyrate (PHB). However, their largescale production remains economically challenging due to the high cost of carbon substrates required for microbial fermentation. Microalgae offer a sustainable alternative owing to their ability to capture CO2 and grow in diverse conditions, yet their intracellular PHA content is typically low, limiting industrial scalability. Utilizing microalgal biomass as a renewable carbon source for bacterial PHA production presents a promising pathway to reduce costs. Nonetheless, limited biorefinery integration, reliance on conventional upstream and downstream methods, and the scarcity of comprehensive life cycle assessment (LCA) and techno-economic analysis (TEA) studies hinder commercialization. This review provides a critical overview of current PHA production strategies using intracellular microalgae and its biomass, identifies key challenges and research gaps, and critically discusses available LCA and TEA studies related to other substrate-based systems. Furthermore, it proposes a conceptual yet promising framework integrating flue gas and wastewater utilization, genetic modulation, green solvent extraction, and circular bioeconomy principles to enhance economic and environmental sustainability. The insights presented herein aim to guide future research toward the scalable and eco-efficient production of PHA from microalgae.

Dairy industries generate large volumes of contaminated wastewater, previous research has focused on finding effective treatment technologies to manage dairy effluent. However, in recent years there has been a shift in focus to recovery of material from wastewater to support circular economy. Various products such as biodiesel, fertilizer, biogas, animal feed, bioethanol, electricity can be recovered from dairy wastewater (DWW) using technologies such as membrane technology, chemical precipitation, anaerobic digestion, algae technology and bio-electrochemical system. The feasibility of using these technologies for material recovery have been studied in wastewater. However, these methods are not widely used in large-scale DWW owing to their challenges such as fouling for membrane, High operational cost for anaerobic digestion, bio-electrochemical and chemical precipitation. Hence, this paper reviews the feasibility, challenges and prospects of applying these technologies in the realm of DWW. Biological recovery methods have gained traction for their potential to recover valuable materials in wastewater and are suggested as sustainable options especially for the recovery of materials in DWW with anaerobic digestion being widely adopted in many DWW treatment plants in Poland. Microalgae have also been widely studied and proposed as an alternative method for recovery of materials in DWW since it offers several benefits such as wastewater treatment and subsequent to material recovery. Although microalgae are a promising option, based on the characteristics of DWW, it cannot be used as a sole recovery technology, it needs to be combined with other treatment technologies to attain maximum treatment and recovery of material from DWW.

The escalating global plastic pollution crisis has intensified the demand for bio-based, biodegradable alternatives, such as polyhydroxybutyrate (PHB). Among various sources, microalgae-derived PHB has emerged as a promising and sustainable biomaterial. This study investigated PHB production in Scenedesmus sp., focusing on growth modes, time intervals, and nutrient optimization to enhance yields. Response surface methodology (RSM) was employed to evaluate the effects of nitrogen (N) and carbon (C) concentrations on PHB accumulation. Heterotrophic cultivation of Scenedesmus sp. over 8 days achieved the highest PHB content compared to phototrophic and mixotrophic modes. Optimization using RSM identified N and C concentrations of 0.409 g L-1 and 1.583 g L-1 , respectively, resulting in a PHB yield of 3.20 +/- 0.28%. Characterization of the recovered biopolymer revealed thermal stability below 230 degrees C, indicating potential applicability in industrial bioplastic production. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of characteristic ester bonds, validating the polymer identity as PHB. Furthermore, pretreatment strategies were explored to improve recovery efficiency, whereby sonication enhanced PHB yield to 4.89 +/- 0.65%. These findings demonstrate that Scenedesmus sp. can serve as a viable microalgal platform for PHB production, with optimization strategies significantly influencing yield outcomes. This study underscores the potential of integrating nutrient regulation and pretreatment techniques to advance microalgae-based bioplastic production and contribute to sustainable solutions for mitigating plastic pollution.

The development of an efficient valorisation of waste-activated sludge (WAS) from wastewater treatment plants (WWTPs) is a sustainable solution to bioresource and bioenergy exploitation. The use of hydrothermal treatment (HT) integrated with anaerobic digestion (AD) to enhance the efficiency of bioresource and bioenergy generation from WAS is the focal area of this research. The HT process was designed under a central composite design, while detoxification via adsorption, precipitation of struvite and biogas production under the AD process were further exploited to enhance the recovery of nutrients and biogas yields. The study has shown improvement in the solubilisation of organic matter after HT, phosphorus recovery, and biogas generation. Consequently, this integration approach offers an optimistic perspective on developing a novel strategy for improving resource recovery from WWTPs. A temperature of 220 degrees C and a residence time of 20 min were found as optimum operating conditions for the HT, and effectively solubilised organics with reported soluble chemical oxygen demand (SCOD) from 613 mg/L to 8474 mg/L. The adsorption using magnetic biochar in the hydrothermally treated sludge was capable of reducing phenolic compounds by 37.9 % and heavy metals-copper, manganese, and nickel by 60.4, 73.5 and, 56.2 %, respectively. This process was also associated with a loss of phosphate and ammonium by 50.3 % and 47.2 %, respectively, through adsorption. The struvite precipitation process resulted in a high overall phosphorus recovery efficiency of 70.52 % and moderate ammonium removal efficiency of 35.71 % under the optimised condition of pH of 9.24 and the addition of 14.2 mL/L of magnesium chloride. The biogas yield was enhanced greatly in hydrothermally treated and detoxified sludge, highlighting the synergy between HT and AD with cumulative methane yields for WAS, HT, adsorption and precipitation streams of 2.3, 72.7, 58.6 and 32.4 mL/g-VS, respectively. Furthermore, the obtained hydrochar with a heating value of 17.8 MJ/kg makes it a viable biofuel source.

Tuberculosis (TB) remains a major public health challenge in sub-Saharan Africa, driven by high transmission, delayed diagnosis, and limited surveillance. This study presents one of the first integrated applications of shotgun metagenomic and metatranscriptomic sequencing to investigate Mycobacterium communities in wastewater across six TB-endemic countries: Cameroon, Ghana, Kenya, Nigeria, South Africa, and Uganda. Twelve untreated and treated wastewater samples were analysed to characterise taxonomic composition, strain-level diversity, and transcriptional activity. Metagenomic analyses revealed diverse Mycobacterium communities, including M. tuberculosis, M. canettii, M. bovis, and members of the M. avium complex. Metatranscriptomic data detected MTBC-associated transcripts, indicating transcriptional activity and/or persistence of MTBC RNA signals in wastewater, with higher signal predominance in influent samples, consistent with community-level shedding. Metagenome-assembled genomes (MAGs) recovered from South Africa, Cameroon, and Uganda showed >82% completeness and included zoonotic species. MTBC strains clustered into Lineages 1, 2, 4, and 6, with animal-adapted strains linked to livestock and rodents, highlighting One Health relevance. Overall, this dual-omics approach supports wastewater-based epidemiology as a scalable tool for TB surveillance in high-burden settings.

Polylactic acid (PLA) waste is an increasing environmental challenge that demands valorization routes aligned with circular bioeconomy principles. This study demonstrates an integrated chemical-biological strategy to upcycle PLA into polyhydroxyalkanoates (PHAs) through two pathways: (i) alkaline depolymerization to lactaterich hydrolysates, acidogenic fermentation to volatile fatty acids (VFAs), and PHA accumulation, and (ii) direct PHA production from lactate-rich chemical hydrolysates. PLA was depolymerized using NaOH pretreatment (0.5-4 M) at 37 and 55 degrees C, achieving >90% carbon solubilization with kinetics governed by alkali strength and particle size. Mixed-culture fermentation converted lactate mainly into propionate and acetate, with hydrolysates produced at 2 M NaOH giving the highest VFA titers and activity. Cupriavidus necator assays revealed stronger interaction between substrate type and nutrient regime for PHA accumulation. VFA-rich streams under nutrientsufficient condition supported the highest biomass and PHA production at 2 M, whereas, lactate-rich hydrolysates under nutrient-deficient (nitrogen-limited) condition yielded maximum PHB content of 84.3% (w/w) at 0.5 M. Comparatively, the direct lactate-based route showed greater practical potential as it enabled higher polymer accumulation while avoiding the intermediate fermentation step required in the VFA-mediated pathway. Overall, the integration of alkaline depolymerization with microbial conversion highlights potential for developing simplified and scalable bioconversion strategies for plastic waste valorization, while supporting sustainable materials recovery within a circular bioeconomy framework.

This review comprehensively evaluates the direct and indirect disinfection mechanisms and performance of chlorine-UV hybrid disinfection (CUV-HD) for the removal of microbial and emerging contaminants, including post-disinfection regrowth and formation potential of disinfection byproducts (DBPs), to ensure safe reuse of treated effluents. Direct disinfection reactions are mediated by HOCl and OCl⁻, as well as UV-induced photolytic damage. In contrast, indirect inactivation is driven by reactive oxygen species (ROS), particularly ∙OH, and reactive chlorine species (RCS) such as Cl∙, ClO∙, and Cl₂∙⁻. The order of reactive species generation indicates UV/chlorine > chlorine–UV > UV–chlorine, which is supported by the effective reduction potential and, consequently, the disinfection efficacy against microbial pollutants in treated wastewater. However, the water matrix, including pH, temperature, organic matter, and total suspended solids (TSS), significantly influences both the disinfection efficiency of these hybrid strategies and the potential formation of disinfection byproducts (DBPs). The formation potential of DBPs follows the order: UV/chlorine > UV–chlorine > chlorine–UV. Further studies quantifying reactive chlorine species (RCS) and elucidating their roles in CUV-HD are needed to fully understand the underlying indirect disinfection mechanisms.

This study engineered a series of novel nickel-doped ceria nanoparticles to assess their supplementation effects on the microalgae Tetradesmus. Nanoparticles (NPs) were synthesized using the co-precipitation method and characterized by various techniques. The synthesized NPs were utilized to assess the effects of different dosages on the physiology (F-v/F-m), chlorophyll-a content, and biochemical composition of T. obliquus growth. Different dosages (5, 10, 20, and 50 mg/L) of 0 %Ni@CeO2, 0.25 %Ni@CeO2 and 0.5 %Ni@CeO2 NPs were added in BG11 for investigation. Results show that 0.25 %Ni@CeO2 (20 mg/L) NPs show the highest (2.19 g/L) biomass production compared to BG11 (1.67 g/L), and other NPs added media. Similarly, the protein content in 0.25 %Ni@CeO2 (20 mg/L) medium was similar to 14 % and 29.74 % higher compared to BG11 and 0 %Ni@CeO2 (5 mg/L) medium. The lipid and carbohydrate content in NPs-supplemented growth media shows a higher yield than BG11. The maximum higher (22.06 MJ/kg) heating value (HHV) was observed in 0.25 %Ni@CeO2 (20 mg/L), followed by 20.67 MJ/kg in 0 %Ni@CeO2 (20 mg/L). Similarly, the highest CO2 fixation rate (0.28 gCO(2)/L/d) was observed in 0.25 %Ni@CeO2 (20 mg/L). This research shows that 0.25 %Ni@CeO2 (20 mg/L) addition in BG11 medium is a promising strategy to enhance microalgae growth, biochemical content, and CO2 sequestration. Furthermore, this study provides a detailed insight into the interaction mechanism between 0.25 %Ni@CeO2 NPs and the microalgal photosystem. The finding might be easily scaled up at the demonstration scale for enhanced biomass production.

Conventional chemical and physical carbon dioxide (CO2) sequestration methods are expensive due to high energy demands, and their long-term environmental implications are still unclear. Microalgae offer a promising alternative solution for efficiently sequestering CO2 to produce biomass, which can be repurposed as natural fertilisers. Microalgal biofertilisers improve soil fertility, boost plant growth and soil microbial diversity, and increase stress tolerance while minimising reliance on synthetic fertilisers. Bio-fertiliser production and utilisation reduce the carbon footprint of traditional fertiliser production. This integrative approach has the capability for ensuring long-term application sustainability, however, it requires the development of cultivation systems for higher photosynthetic efficiency and biomass productivity, reduction in nutrient and water requirements, and addressing the need for substantial capital investment. This study aimed to assess the feasibility of microalgal carbon sequestration and examine its economic and environmental benefits. Microalgae-based systems not only capture CO2 efficiently but also offer viable commercial application of the resultant biomass. This creates possible monetary incentives for corporations to invest in microalgal CO2 sequestration to offset carbon emissions. Numerous funding sources are available for microalgal cultivation projects focusing on CO2 sequestration while promoting biomass valorisation. The environmental and economic considerations with the exploration of wastewater integration and policy are reviewed to address the developmental challenges in implementing microalgal CO2 sequestration for bio-fertiliser production. A circular economy integrating research and development, robust strain/s selection, infrastructure and logistics, etc, for CO2 sequestration and bio-fertiliser generation is suggested. This strategy will contribute to a long-term, balanced approach to CO2 mitigation, benefiting agricultural productivity.

High-value microalgal metabolites have attracted attention but been confined largely to lab scale experiments. A small number of success stories stand as a testimonial to the fact that, despite higher yields and promises of being sustainable, they are presently cost intensive and unattractive to the industry. This study attempts a media engineering approach using chemical modulators for targeted biomass and metabolite enhancement. We investigated 55 compounds over a 2-phase study for targeted improvements in biomass, α-linolenic acid (ALA), or α-tocopherol productivities. Salicylic, indole butyric, gibberellic, and benzoic acids stimulated growth by ∼ 12.43 – 20.28 % at concentrations of 20 – 1000 nM. Fucose, β-ionone, auxins, and gibberellic and ascorbic acids had ∼ 20.75 – 75.44 % better ALA productivity between 20 – 100 nM while β-ionone, kinetin, and benzoic acid stimulated α-tocopherol by ∼ 44.88 - 109.33 % at 100 - 1000 nM, compared to control. A basic economic analysis showed that biomass, ALA and α-tocopherol together could make the process economically attractive. Auxins, β-ionone, salicylic, and ascorbic acids were feasible considering the input cost vs. revenue generation potential while kinetin, cyanocobalamin, 3-hydroxydecanoic, folic, and oxaloacetic acids were deemed uneconomical.

The virtues of omega-3-polyunsaturated fatty acids (ω-3-PUFAs) have garnered considerable acclaim owing to their multifaceted human health benefits. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) represent long-chain ω-3-PUFAs synthesized from the precursor α-linoleic acid (ALA). Conventionally, fish, shellfish, and krill have been the primary sources of omega-3 fatty acids. However, with declining marine stocks and increasing demand from vegan populations, there is a growing need for alternative, sustainable sources. This review aims to critically evaluate and consolidate recent advances in microalgal biotechnology for enhancing the production of ω-3-PUFAs from microalgae. This comprehensive review work covers diverse techniques from abiotic stress and nutrient manipulations to enhance lipids as well as ω-3-PUFA contents to sophisticated metabolic engineering approaches aimed at augmenting ALA, EPA, and DHA levels in microalgae. The article emphasizes the use of genetic engineering techniques, focusing on innovative gene editing tools such as RNA interface (RNAi), clustered regularly interspaced short palindromic repeats (CRISPR-Cas9), and transcription activator-like effector nucleases (TALEN) for the manipulation of key lipid/ fatty acid biosynthesis enzymes. Emphasis is placed on the scalable cultivation systems (e.g., photobioreactors, raceway ponds) and eco-friendly downstream processes like green solvent extraction and molecular distillation. Overall, this review highlights the growing potential of microalgal biotechnology to sustainably meet the rising global demand for ω-3-PUFAs and provides insights for future research toward large-scale, eco-friendly ω-3-PUFA production.

In aquatic ecosystems microplastics (MPs) provide new habitat for microbes, forming the plastisphere. While, the effect of different pollution sources on microbiome compositions, functions and assembly processes remains largely cryptic, and hence requires further investigation. Thus, in this study microplastic and surrounding water samples were collected from four different locations and performed meta-analysis to evaluate the impact of different pollution sources on microbial community composition, function and assembly in plastisphere and surrounding environment. Results demonstrated that pollution source had a significant effect on microbial diversity (p = 0.0012) and composition (PERMANOVA F = 16.386; R-2 = 0.15, p < 0.001) in surface water and plastisphere. Specifically, plastisphere harboured distinct microbial community and recruited unique taxa compared to surface water, suggesting that microplastics serve as new ecological habitats. We observed a clear shift in microbial community composition, with Bacteroidetes being significantly higher in surface water significantly, whereas alpha- and beta-Proteobacteria dominated the plastic surface (p < 0.05). These change in microbial communities were more likely due to unique chemical properties and substrates enrichment on plastic surfaces and different pollution sources. Genes involved in metabolism, signaling, cell motility, vesicular transport energy production and defence were significantly enriched in plastisphere (p = 0.001). The environmental factors such as DO and salinity drive the microbial communities in plastisphere. Niche-based selection process govern assembly in plastisphere microbiome, while as stochastic processes dominated the assembly process in aquatic microbial communities. These finding suggest that trajectory, continued microplastic emission and transport in aquatic ecosystems could pose serious planetary and health issues.

Tuberculosis (TB), especially in its drug-resistant form, remains a critical public health challenge in sub-Saharan Africa, where conventional airborne transmission has been well-characterized. However, wastewater systems prevalent across urban centres may serve as overlooked environmental reservoirs for Mycobacterium tuberculosis, posing occupational and environmental health risks. Despite this, the health implications of wastewater exposure remain underexplored, particularly in high TB-burden settings. To address this research gap, we applied the Quantitative Microbial Risk Assessment (QMRA) framework, incorporating Disability-Adjusted Life Years (DALYs), to assess the health risks of exposure to drug-resistant TB pathogens in wastewater. Our study uniquely focuses on three exposure scenarios: untreated wastewater at the head of works, aerosols from aeration tanks, and reuse of treated wastewater for irrigation, across six African countries: Ghana, Nigeria, Kenya, Uganda, Cameroon, and South Africa. The study found the highest concentrations of M. tuberculosis in Ghana, with rifampicin-resistant strains present at lower levels across all countries. Infection risks ranged from 3 % to 100 %, with irrigation posing the highest median infection risk (0.77). The greatest disease burdens were observed at the head of works (112.46 DALYs) and during irrigation (105.31 DALYs). Our findings highlight wastewater as a significant and previously underestimated route for TB transmission. This study underscores the urgent need for enhanced treatment technologies, occupational safety protocols, and environmental surveillance. Integrating wastewater-based epidemiology into national TB monitoring could provide a valuable early-warning system, especially in regions reusing wastewater for agriculture, and may significantly strengthen global TB control strategies.