Abstract
Background/Objectives: Sap from Nypa fruticans are used as feedstock for a bioethanol national program to establish a sustainable and productive village-scale bioethanol industry. The study aimed to establish the physicochemical, microbiological, and molecular characteristics of nipa sap. Methods/Statistical Analysis: Nipa sap samples were collected from three sampling sites at different fermentation time. Physico-chemical parameters such as pH, titratable acidity, and total soluble solids were determined and statistically analyzed using One-way Analysis of Variance and mean ± SD values. Molecular approaches were used to profile and identify yeast species naturally residing in the sap during fermentation and assess the genetic diversity of nipa palm in selected sampling locations. Findings: Sampling site and fermentation time significantly affect the levels of pH, titratable acids, and total soluble solids in the sap samples. Sugar concentration in nipa sap is affected by sampling site: as the sampling site nears the river, the amount of sugars become significantly greater. Molecular studies revealed that among the 12 isolates obtained, five of them (Y24S1, Y48S1, Y72S1, Y24S2, and Y24S3) showed 100% similarity to strain of Pichia occidentalis, three (Y48S2, Y48S3, and Y72S3) were similar (100%) to a strain of Saccharomyces cerevisiae (YPDW9), and the other two isolates (Y72S1 and Y48S3A) were identical to Naganishia randhawae strain HBUMO6885 and Tremellales sp. LM523 respectively with a 100% similarity. PCR amplification of their trnL–trnF cpDNA genome, BLAST and phylogenetic analyses reveals that all nipa plant samples were similar to Nypa fruticans. Applications: The generated information on the effect of sampling site on sugar content of nipa sap samples could be good input in selecting expansion sites for the establishment of nipa plantations. Furthermore, the identified yeast strains can be used as inoculant or starter culture to improve fermentation. Keywords: Physico-chemical parameter; yeasts molecular profiling; nipa sap fermentation; phylogenetic analysis; genetic diversity
Highlights
Nipa palm (Nypa fruticans) is the most promising of first-generation feedstocks owing to its advantages over other fuel crops
Results revealed that sampling site and fermentation time significantly affect the pH levels of the sap samples, but there is no significant difference between the pH levels of the sap and the combined interaction of the effects of sampling site location and time ( Table 1)
Nipa sap collected in a place where the nipa plant is always submerged in water have a significant lower pH mean values, which is significantly more acidic than the pH of the samples collected from the two other sites ( Table 1)
Summary
Nipa palm (Nypa fruticans) is the most promising of first-generation feedstocks owing to its advantages over other fuel crops. It does not compete with food crops for land and water resources because it thrives where most crops cannot grow; second, it requires very little maintenance because once established, it will last for at least 50 years - in contrast with all other sources of bioethanol that need to be replanted after harvest; third, it has many other uses in such innovative systems as aquasilviculture designed to rehabilitate abandoned fishponds where fishery and nipa production complement each other [1,2]. Nypa fruticans is known to continuously produce rich sugar-sap from its infructescence for over 50 years. Fermented palm sap contains low molecular mass carbonyls (C1 -C6) as by-products of yeast fermentation, and alcoholic oxidation at various stages of fermentation [4]
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