Asian Journal of Applied Chemistry Research

Lignocellulosic Pretreatment in Integrated Biofuel Systems: Linking Biomass Chemistry, Microbial Dynamics, Reactor Engineering, and AI-Driven Optimization for Bioethanol and Biomethane Production

Philimon Dickson Nganyira — 2026-09-16

Global efforts to decarbonise energy systems have intensified interest in lignocellulosic biofuels such as bioethanol and biomethane as complementary components of a diversified renewable energy portfolio. However, the recalcitrant architecture of lignocellulosic biomass, dominated by lignin, cellulose and hemicellulose networks remains a fundamental barrier to efficient hydrolysis and microbial conversion. Although numerous pretreatment technologies have been developed to address this challenge, existing reviews largely examine these strategies in isolation from downstream bioconversion processes and reactor engineering constraints. The present review provides an integrated synthesis of lignocellulosic pretreatment within the broader biofuel production system, linking biomass chemistry, microbial community dynamics, process engineering and emerging computational optimisation approaches. It evaluates physicochemical, biological and hybrid pretreatment strategies and analyses their impacts on hydrolysis efficiency, biomethane and bioethanol yields and process stability across diverse feedstocks. Particular attention is given to recent advances in co-digestion strategies, microbial community management, artificial intelligence-assisted process optimisation and innovative reactor configurations that enable improved conversion performance. By integrating biochemical mechanisms with engineering and data-driven perspectives, the review identifies critical technological bottlenecks. It proposes a systems-oriented framework for enhancing process efficiency, stability and techno-economic feasibility. These insights provide strategic directions for the development of next-generation lignocellulosic biorefineries capable of supporting scalable and sustainable biofuel production.

Heavy Metal Contamination of African Leafy Vegetables Grown in Urban and Peri-Urban Agricultural Systems- A Review

Rachael N. Nyagaka — 2026-09-19

Urban and peri-urban agriculture is the major source of the fresh produce sold in African cities, including indigenous African leafy vegetables such as Solanum nigrum, Cleome gynandra, and Vigna unguiculata. Many urban and peri-urban agricultural activities are practiced close to wastewater sources, industrial activities, major roads, and waste dumps, exposing the vegetables to cadmium, lead, chromium, nickel, copper, zinc, arsenic, and mercury contamination. Reported concentrations of heavy metals vary widely with irrigation practice, soil characteristics, contamination source, and vegetable species. Cadmium and lead are the metals most frequently reported to exceed food safety limits. Additionally, chromium and zinc have also been noted to exceed safe limits in wastewater-irrigated and roadside-cultivated vegetables. This review examines the soil and plant factors governing metal uptake and evaluates human health risks using Target Hazard Quotient, Hazard Index, and Lifetime Cancer Risk approaches. This study highlights the significant risks posed by the presence of heavy metals in vegetables and emphasizes the importance of stringent environmental monitoring and the implementation of appropriate regulatory mechanisms for human health and environmental risk mitigation. Comparability across studies remains limited by inconsistent health-risk-assessment parameters and uneven geographic and species coverage, with several widely consumed African leafy vegetable species and West, Central, and North African countries remaining underrepresented in the reviewed literature. The findings could help formulate appropriate policy implementation strategies aimed at mitigating heavy metal contamination in Africa’s food supply. However, further research is needed to cover underutilized vegetable species. Moreover, studies from more countries should be included in future research.

COF-10 as a Mesoporous Host for Solid-State Ionic Conduction of Lithium Iodide

Boris Irié-Bi — 2026-09-16

Covalent organic frameworks (COFs) provide structurally defined porous environments for solid-state ion transport, yet the extent to which a chemically neutral framework can modify the transport properties of an incorporated inorganic salt remains poorly understood. This study evaluates mesoporous boronate-ester COF-10 as a neutral host for lithium iodide (LiI) and examines the structural and electrochemical consequences of LiI incorporation. LiI incorporation preserves the covalent framework while strongly modifying its accessible porosity, decreasing the characteristic pore diameter from approximately 34.1 to 18.3 Å. The resulting COF-10@LiI composite exhibits an ionic conductivity of 1.44 × 10⁻⁶ S cm⁻¹ at 20 °C, which increases markedly with temperature and remains higher than that of LiI when measured under comparable conditions throughout the investigated temperature range. Potentiostatic polarisation at 100 °C yields an apparent lithium-ion transference number of approximately 0.63, indicating a substantial Li⁺ contribution while confirming mixed-ion transport. An oxidative current onset is observed near 2.9 V vs Li/Li⁺ under the measurement conditions, enabling evaluation with a low-voltage lithiated benzoquinone electrode, for which repeated lithium insertion and extraction are sustained over consecutive cycles despite significant polarisation. Together, these results show that incorporation of LiI into the mesoporous environment of a neutral COF modifies the transport behaviour of the salt and supports functional solid-state lithium transport. COF-10 therefore provides a structurally defined model platform for investigating how mesoporous confinement and host–guest interactions can regulate ionic transport in COF-based solid electrolytes.

Low-molecular-weight Polycyclic Aromatic Hydrocarbons as Indicators of Petroleum Contamination and Ecological Risk in Ataba–bodo Estuary Sediments, Niger Delta

Angela Atata — 2026-09-22

Background: Polycyclic aromatic hydrocarbons (PAHs) are persistent organic contaminants capable of accumulating in aquatic sediments and posing ecological concerns in estuarine environments exposed to petroleum-related and other anthropogenic activities. The Ataba–Bodo estuarine environment occurs within the Niger Delta, where intensive human activities may influence sediment quality.

Aim: This study assessed the occurrence, spatial distribution, compositional characteristics and ecological risk associated with five low-molecular-weight PAHs in sediments of the Ataba–Bodo estuary, southern Nigeria.

Materials and methods: Surface sediment samples were collected from eight stations comprising four stations at Ataba and four at Bodo. Three replicate samples were collected per station. Samples were prepared and extracted for chromatographic determination of naphthalene, acenaphthylene, acenaphthene, fluorene and phenanthrene. Concentrations were expressed as µg/kg dry sediment. The total concentration of the five target compounds (Σ5LMW-PAHs), the relative contributions of individual compounds and spatial distribution were determined. Ecological risk was evaluated using the risk quotient approach.

Results: All five target LMW-PAHs were detected across the sampling stations. Naphthalene was the dominant compound, with concentrations ranging from 31.45 ± 0.63 to 89.62 ± 1.78 µg/kg, followed by phenanthrene, which ranged from 29.64 ± 0.61 to 71.46 ± 1.39 µg/kg. The Σ5LMW-PAH concentration ranged from 81.27 ± 0.93 µg/kg at ATB-3 to 221.07 ± 2.42 µg/kg at BOD-2. The mean Σ5LMW-PAH concentration was higher at Bodo (171.97 ± 42.67 µg/kg) than at Ataba (123.53 ± 38.91 µg/kg). Naphthalene contributed 38.7–40.8% of the total measured burden, while phenanthrene contributed 32.3–36.5%. Ecological risk quotients ranged from 0.14 at ATB-3 to 0.39 at BOD-2, with all stations classified as low risk under the adopted risk framework.

Conclusion: The sediments of the Ataba–Bodo estuary contained measurable concentrations of the five investigated LMW-PAHs, with a greater overall burden observed in Bodo than in Ataba. Naphthalene and phenanthrene were the principal contributors to the measured PAH burden. Although the calculated ecological risk remained low at all stations, the comparatively elevated concentrations and risk quotient at BOD-2 identify this location as a priority for continued environmental monitoring.

Influence of Nitrogen Fertiliser Rates on the Amino Acids Composition in African Nightshade (Solanum scabrum) Young Leaves

Russ Dan Ochieng — 2026-09-23

African leafy vegetables are important sources of dietary nutrients, including amino acids, but agronomic factors can influence their nutritional composition. Such nutrients include amino acids (AAs), which play important roles in human health, and some of their by-products are implicated in the management of lifestyle diseases. For example, gamma-aminobutyric acid (GABA) from glutamic acid (GA) is implicated in the management of both hypertension and diabetes. African leafy vegetables (ALVs) are consumed within poor communities where the disease burden is grave. The potential use of ALVs to manage lifestyle diseases is not acknowledged. African nightshade (Solanum scabrum) is among the most consumed ALVs in western Kenya. However, agronomic methods for enhancing AA levels in African nightshade are not well documented. Nitrogen fertilisers have been documented to enhance AA levels in some plants. The influence of nitrogen rates on the AA composition of African nightshade was investigated. The trial was laid out in a randomised complete design with three replications, with nitrogen (urea) rates (0, 50, 100 and 150 Kg N/ha) as treatments. The young leaves were harvested after six weeks, processed and analysed for AAs using LC-MS. A total of fourteen AAs were detected, with leucine > GA > isoleucine as the main AAs. Levels of all AAs increased (p ≤ 0.05) with increasing nitrogen rates. The presence of high levels of GA in African nightshade suggests its potential use in the production of GABA-rich vegetables in the human diet. GA is readily decarboxylated to GABA when the vegetable is subjected to milk treatment or kept under anaerobic conditions. The use of high rates of nitrogenous fertiliser is recommended as an agronomic technology to enhance levels of beneficial AAs in African nightshade.

Heavy Metal Release Potential of Selected Dumpsite Waste Streams: Geochemical Evidence and Assessment of Soil Pollution Indices

Bassey U. Udo — 2026-09-24

The release of potentially harmful metals from waste materials into soil represents a significant pathway for soil contamination. This study quantitatively examined the release potential of metals (Cd, Cr, Ni, Pb, and V) from diverse waste streams at predetermined depths (0–20 cm and 20–40 cm). The principle of mass balance was employed to assess waste-metal release potential, with contamination factor (CF), metal pollution index (MPI), and pollution load index (PLI) employed as pollution indicators. Findings indicated that the investigated wastes caused significant pollution within the studied soils, with automechanic- and paint-related wastes having the highest metal-release potentials. The mean natural background concentration of lead in the studied soils was 7.0 mg/kg. Automechanic wastes elevated this concentration by 529 times, while paint- and abattoir-related wastes increased it by 197 and 8.4 times, respectively. CF values across the investigated dumpsite soils and depths revealed severe contamination, particularly for chromium, with values reaching 972.36. MPI values indicated substantial multi-metal contamination, with a PLI peak of 292.58. High contamination levels were not confined to the topsoil, as some locations recorded elevated concentrations of Pb and Cr at 20–40 cm depth, suggesting either downward migration of the contaminants through the soil profile or burial of originally contaminated topsoil during land filling. All affected soils showed excessive pollution, while the different waste streams exhibited varying capacities to release heavy metals into soil. These results underscore the need for source-specific waste management and improved strategies to mitigate ongoing contamination and associated risks.