Biodiesel potential of Cucumeropsis mannii (white melon) seed oil: A neglected and underutilized resource in Nigeria.

A major challenge in the biodiesel industry is the availability of high-quality vegetable oil feedstocks. Thus, there is a continuous search for quality biodiesel feedstock whose production will trigger economic impact on the agricultural sector, minimize land degradation and without significant disruption to the food chain. In this work, we extracted and analysed oil from neglected and underutilized Cucumeropsis mannii seeds for their potential in biodiesel production. The oil content of C. mannii seed was 40.8 ± 0.56%. GC-MS analysis of the oil revealed the presence of 47.0% saturated fatty (predominantly palmitic acid, stearic acid) and 53.0% of unsaturated fatty acids (predominantly oleic, linoleic and erucic acids). The physicochemical properties were determined and values were as follows: iodine value (111.07 ± 0.15 g/100 g), saponification value (192.03 ± 0.37 mg/kg of oil), peroxide value (2.60 ± 0.10 meq/kg), acid value (4.20 ± 0.02 mgKOH/g) free fatty acid (2.51 ± 0.02%), relative density (0.93 ± 0.02), the refractive index at 28 °C (1.46 ± 0.04) and viscosity at 30 °C (3.00 ± 0.10 mm2/s). The fuel properties namely, cloud point, pour point, flash point and caloric value were determined and the values were 3.03 ± 0.11 °C, 1.00 ± 0.10 °C, 279.04 ± 0.99 °C and 31.10 ± 0.11 MJ/kg, respectively. In addition, the protein content of the defatted seed was found to be 47.4 ± 0.61 g/100 g. The defatted protein-rich cakes can be upgraded as a food additive; thus the C. mannii seed oil can serve as biodiesel feedstock without altering the food chain. These characteristics demonstrate the potential of C. mannii oil as a high-quality feedstock for biodiesel production. We envisage that its utilization as biodiesel feedstock will improve the market value of these seeds, thus supporting the economic development of local farmers in rural areas.

Bioinformatic characterization of a triacylglycerol lipase produced by Aspergillus flavus isolated from the decaying seed of Cucumeropsis mannii.

Lipases are enzymes of industrial importance responsible for the hydrolysis of ester bonds of triglycerides. A lipolytic fungus was isolated and subsequently identified based on the ITS sequence analysis as putative Aspergillus flavus with accession number LC424503. The gene coding for extracellular triacylglycerol lipase was isolated from Aspergillus flavus species, sequenced, and characterised using bioinformatics tools. An open reading frame of 420 amino acid sequence was obtained and designated as Aspergillus flavus lipase (AFL) sequence. Alignment of the amino acid sequence with other lipases revealed the presence GHSLG sequence which is the lipase consensus sequence Gly-X1-Ser-X2-Gly indicating that it a classical lipase. A catalytic active site lid domain composed of TYITDTIIDLS amino acids sequence was also revealed. This lid protects the active site, control the catalytic activity and substrate selectivity in lipases. The 3-Dimensional structural model shared 34.08% sequence identity with a lipase from Yarrowia lipolytica covering 272 amino acid residues of the template model. A search of the lipase engineering database using AFL sequence revealed that it belongs to the class GX-lipase, superfamily abH23 and homologous family abH23.02, molecular weight and isoelectric point values of 46.95 KDa and 5.7, respectively. N-glycosylation sites were predicted at residues 164, 236 and 333, with potentials of 0.7250, 0.7037 and 0.7048, respectively. O-glycosylation sites were predicted at residues 355, 358, 360 and 366. A signal sequence of 37 amino acids was revealed at the N-terminal of the polypeptide. This is a short peptide sequence that marks a protein for transport across the cell membrane and indicates that AFL is an extracellular lipase. The findings on the structural and molecular properties of Aspergillus flavus lipase in this work will be crucial in future studies aiming at engineering the enzyme for biotechnology applications.Communicated by Ramaswamy H. Sarma.

Biochemical characterization of Soxhlet-extracted pulp oil of Canarium schweinfurthii Engl. fruit in Nigeria.

Characterization and further development of underutilized/underexploited indigenous tropical seed oils are essential to supplement both nutritional and industrial needs of an ever-increasing African (and global) population. Before now and to our best knowledge, the previous research involved Canarium schweinfurthii Engl. fruit specific to Nigeria appear to have been more on the evaluation of seed, pulp, and essential oils (from the seed), but much less on the pulp oil. To supplement existing information, this current work has aimed to biochemically characterize the Soxhlet-extracted pulp oil of C. schweinfurthii fruit gathered from a community situated in the South-east of Nigeria. Specifically, the biochemical characterization comprised the determinations of proximate compositions, lipid peroxidation, fatty acid profile, as well as carotenoids, sterols, and tocopherols. Processing the fruit sample to pulp oil involved, among others, oven-drying, and grinding, prior to the Soxhlet extraction. Results of proximate components of C. schweinfurthii pulp oil showed the following trend: crude fat content (~ 49.32%) > carbohydrates (~ 37.93%) > moisture content (~ 8.62%) > ash content (~ 3.74%) > crude protein content (~ 0.39%) values. The lipid peroxidation attributes comprised acid (~ 23.60 mg KOH/g), peroxide (~ 33.91 mEq. O2/kg), iodine (~ 58.3 g/100 g), and saponification (~ 138.21 mg KOH/g) values. In addition to the free (~ 13.8%), saturated (~ 9.74%), and unsaturated (~ 90.26%) fatty acids, a total of fifteen (15) fatty acid methyl esters (FAMEs) spectral peaks were found, from caprylic acid (C8:0) to lignoceric acid (C24:0). Total tocopherol concentration amounted to ~ 73 mg/100 g, which comprised α, ß, γ-tocopherol, and δ-tocotrienol, with fair concentrations of carotenoids and sterols. Overall, the C. schweinfurthii pulp oil-biochemically competitive with a high concentration of unsaturated fatty acid, tocopherol, and sterol, suggests strong industrial promise.

Quantification of Heavy Metals and Pesticide Residues in Widely Consumed Nigerian Food Crops Using Atomic Absorption Spectroscopy (AAS) and Gas Chromatography (GC).

More still needs to be learned regards the relative contamination of heavy metals and pesticide residues, particularly those found in widely consumed Nigerian food crops like cereals, vegetables, and tubers. In this current study, the heavy metals and pesticide residues detectable in widely consumed Nigerian food crops were respectively quantified using atomic absorption spectroscopy (AAS) and gas chromatography (GC). Specifically, the widely consumed Nigerian food crops included cereals (rice, millet, and maize), legume (soybean), tubers (yam and cassava), as well as leaf (fluted pumpkin, Amaranthus leaf, waterleaf, and scent leaf) and fruit vegetables (okro, cucumber, carrot, and watermelon). Results showed that the detected heavy metals included arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), iron (Fe), lead (Pb), manganese (Mn), mercury (Hg), and nickel (Ni), whereas the pesticide residues included Aldrin, Carbofuran, g-chlordane, Chlorpyrifos, DichloroBiphenyl, Dichlorodiphenyldichloroethane (DDD), Dichlorodiphenyltrichloroethane (DDT), Dichlorvos, Endosulfan, Heptachlor, Hexachlorobenzene (HCB), Isopropylamine, Lindane, t-nonachlor, and Profenofos. Across the studied food crops, the concentrations of heavy metals and pesticides were varied, with different trends as they largely fell below the established maximum permissible limits, and with some exceptions. Our findings suggest there could be a somewhat gradual decline in the concentration of the heavy metals and pesticide residues of these studied food crops when compared to previously published reports specific to Nigeria. To help substantiate this observation and supplement existing information, further investigations are required into the concentration of these heavy metals and pesticide residues specific to these studied food crops at other parts of the country.