| Lotus seed peel waste (LSPW), a by-product of polished lotus seed, consistsmainly of starch, cellulose and proteins. However, the byproduct is underutilized andusually dumped off as waste or simply used as a low-profit fertilizer or animalfeedstuff. If discarded as waste, the byproducts may cause environmental problemsdue to their accumulation. Therefore, in order to solve the environmental problem ofthe waste disposal and provide added value for the byproduct, alternative uses for thebyproduct should be identified. Examples include extraction of phenolicphytochemicals for use in functional foods, and fermentation of starch to ethanol.Firstly, lotus seed peel waste (LSPW) were hydrolyzed with HCl and fermentedby Saccharomyces cerevisae to determine fermentability and ethanol production. Thefinal reducing sugars concentration in the hydrolyzate depended on the concentrationof acid and the ratio of plant material to acid solution. A60min treatment with6%(v/v) HCl at a solid to acid solution ratio of1:6(w/v) was enough to hydrolyze almostall starch in the peel waste. The ethanol yield of25.10g/L was obtained in thefermentation of hydrolyzate prepared under the optimal hydrolysis conditions bycommercial bakery yeast at30℃for about48h. Simultaneous saccharification andfermentation (SSF) of lotus seed peel waste was also carried out for ethanolproduction. Starch in the waste was liquefied to maltodextrins by the action ofthermo-stable α-amylase at50℃. SSF of liquefied mixture was performed with thesimultaneous addition of glucoamylase and yeast (Saccharomyces cerevisiae). Theoptimal glucoamylase loading, fermentation temperature and fermentation time were250u/g,32℃and72h, respectively, obtained using the response surfacemethodology (RSM). Using the optimized condition, ethanol yield of48.65g/100gsugar was achieved, which was equivalent to95.20%of the theoretical yield. Theseresults demonstrate that LSPW features a high potential for ethanol production.Secondly, the antioxidant activity of methanol extract (ME) and ethanol extract(EE) from LSPW was investigated by employing various established systems in vitroincluding2,2’-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, hydroxylradical scavenging assay and reducing power. ME and EE showed excellentantioxidant in all test systems and the antioxidant activities of EE were all superior tothose of ME. The total phenolic content of ME and EE were51.47mg/g and99.7mg/g, respectively, expressed as gallic acid equivalents, which were quantified using Folin–Ciocalteu reagent. Furthermore, the suitability of EE as substitute of BHT weredetermined in rapeseed oil, and the decrease of lipid oxidation were monitored bymeasuring peroxide value (POV), p-anisidine value and conjugated dienes value of oilsamples. EE treatment significantly (P <0.05) reduced lipid oxidation in rapeseed oilcompared to the control. Moreover, oils with0.1and0.3%EE were significantly (P <0.05) superior to0.02%BHT in reducing oxidation of rapeseed oil.Lastly, pectin polysaccharide was extracted from LSPW using ammoniumoxalate aqueous solution as the extraction solvent. Effects of extraction conditionssuch as extraction temperature, ratio of solid to solvent, concentration of ammoniumoxalate and extraction time on the extraction yield were studied in detail. Also, theorthogonal experiment design was used to optimize the extraction conditions. It wasfound that extraction temperature had the highest influence on extraction yieldfollowed by the ratio of solid to solvent, extraction time and concentration ofammonium oxalate. The optimal extraction conditions are as follows: extractiontemperature100℃, ratio of solid to solvent1:30(w/v), concentration of ammoniumoxalate0.7%and extraction time2h. Under these conditions, the extraction yield12.5%is highest. The obtained extract was identified as low methooxyl pectin byFTIR. |
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