Effects of Ebony (Diospyros mollis Griff), White Meranti (Shorea roxburghii G. Don) and Resak Tembaga (Cotylelobium lanceolatum Craib) on Microbes in Palm Nectar Using
Abstract:
The purposes of this research were: 1) to study the compositions of ebony (Diospyros mollis Griff) , white meranti (Shorea roxburghii G. Don) , and resak tembaga ( Cotylelobium lanceolatum Craib) affecting the fermentation of palm nectar and 2) to examine the effects of ebony, white meranti and resak tembaga on the microbial changes during the fermentation of palm nectar using metagenomics technique.
Compositions of ebony, white meranti and resak tembaga were determined by analyzing phenolics, flavonoids, nitrogen, and protein contents. Effects of ebony, white meranti and resak tembaga on the microbial changes during fermentation of palm nectar were studied using metagenomics technique. There were five fermentation treatments. These were fermentation of palm nectar only (control) and fermentations with the addition of white meranti, fresh ebony, roasted ebony, and resak tembaga. Microbial growth during fermentation was observed by plating fermenting nectar on Dicholran Rose Bengal Chloramphenicol Agar (DRBC Agar) and Plate Count Agar with 0. 01 % cycloheximide. Titratable acidity, pH, total soluble solids and ethanol concentrations were measured during the course of fermentation. Colonies of yeasts and bacteria were selected and identified by nucleotide sequencing. Microbial sediments were collected from all fermentation treatments and analyzed using metagenomics technique.
The results revealed that: 1) the three types of wood had statistically significant difference (p<.05) in the amounts of phenolic compounds. White meranti had the highest content at 288.73 mg GAE/g, followed by resak tembaga, roasted ebony, and fresh ebony with 282.60, 130.50, and 50.47 mg GAE/g, respectively. The nitrogen content of resak tembaga was the highest at 3.096 TN%, followed by fresh ebony, white meranti and roasted ebony at 1.566, 1.270, and 0.866 TN%, respectively. The highest levels of flavonoid content were resak tembaga at 45.847 mg QE/g followed by white meranti, fresh ebony, and roasted ebony at 40.941, 35.529, and 32.391 mg QE/g, respectively. There was no statistically significant difference (p<.05) of protein contents among the various kinds of woods, with the highest value being 0.828 %. 2) Effects of ebony, white meranti, and resak tembaga on the microbial changes during palm nectar fermentation showed that the control had higher bacterial growth during 3 days of fermentation than the other four treatments with the addition of woods, and gave higher amounts of acid, slower reduction of total soluble solids, and lower ethanol concentrations, except for resak tembaga which had the lowest ethanol concentration (0.11 %v/v). Fermentations with white meranti and roasted ebony yielded the highest ethanol concentrations (3.42 and 3.28 %v/v, respectively). After three days of fermentation the most common yeasts revealed by metagenomics technique were Saccharomyces cerevisiae (88.5 %), Lachancea fermentati (15.7 %), Candida tropicalis (12.1 %), Hanseniaspora opuntiae (3.2 %) and Hanseniaspora vineae (0.7 %). These results corresponded with those obtained by nucleotide sequence analysis. Phenolic compounds in these woods could help reduce bacterial contamination and the nitrogen compounds help the growth of yeasts, resulting in more efficient alcoholic fermentation.