Nadia Yousaf, MPhil(Zoology) 2016-2018 Supervised by Dr.Asma Chaudhary
Processing of Watermelon Waste for Biothanol Production by Applying Biorefinery Concepts
/Nadia Yousaf
- Lahore : Department of Zoology, Div. S&T University of Education, 2018
- 208 p. xxiii CD
Ethanol and other value added products from agricultural wastes are now focusing area in bioenergy field and to reduce the environmental pollution. The fruit wastes are highly biodegradable; therefore, they could be preserved by drying and may well be used for further processing for a long time. The watermelon is usually consumed throughout the summer. The usage of watermelon in summer produced huge amount of wastes every year. There is dire need to manage this waste because of easy degradation and causing pollution in environment. The study investigated the potential of yeast isolates to convert the watermelon hydrolyzate to ethanol and optimization of hydrolysis condition. Response surface methodology (RSM) using Central Composite Design at 23 factorial level. In optimization, variable factors were alkali concentration (X1), hydrolysis temperature (X2), and hydrolysis time (X3) whereas the responses were reducing sugars, total carbohydrates, weight loss, extractives, hemicellulose, lignin and cellulose contents. Different alkalis i.e. sodium hydroxide (NaOH), potassium hydroxide, (KOH) and calcium hydroxide (Ca(OH)2) were used to hydrolyse watermelon peels. In sodium hydroxide hydrolyzate, the observed optimum values (%) were 5.23±0.02, 17.99±0.01, 16.31±0.02, 34.31±0.04, 24.21±0.01, 9.98±0.01, 10.78±0.02, for reducing sugars, total carbohydrates, weight loss, extractive, hemicelluloses, lignin and cellulose contents at 0.05% NaOH concentration, 100ᵒC temperature and 30 minutes hydrolysis time. The experimental values were more than the predicted values in reducing sugars but less in other responses. This model is significant for reducing sugars and total carbohydrates but non significant for other responses with the F value less than 4 and R2 value varied from 0.5-0.7. On the basis of results, 5.23 percent reducing sugars were recorded with (16.31) percent weight loss. In potassium hydroxide hydrolyzate, the observed optimum values (%) were 4.57±0.02, 22.01±0.03, 13.90±0.01, 19.42±0.00, 24±0.01, 17.99±0.02, 13.28±0.02, for reducing sugars, total carbohydrates, weight loss, extractive, hemicelluloses, lignin and cellulose contents at 0.05% KOH concentration, 60ᵒC temperature and 60 minutes hydrolysis time. The experimental values were more than the predicted values in reducing sugars but less 2 in other responses. This model is not significant for all responses with the F value less than 4 and R2 value varied from 0.5-0.7. On the basis of results, 4.57 percent reducing sugars were recorded with (13.90) percent weight loss. In calcium hydroxide hydrolyzate, the observed optimum values (%) were 4.01±0.01, 26.58±0.03, 18.73±0.02, 15.70±0.01, 13.61±0.02, 26.48±0.01, 11.56±0.01, for reducing sugars, total carbohydrates, weight loss, extractive, hemicelluloses, lignin and cellulose contents at 0.15% KOH concentration, 100ᵒC temperature and 60 minutes hydrolysis time. The experimental values were more than the predicted values in total sugars, extractive, hemicellulose and lignin but experimental values were less than the predicted values in reducing sugars, weight loss and cellulose. This model is not significant for all responses with the F value less than 4 and R2 value varied from 0.5-0.7. On the basis of results, 4.01 percent reducing sugars were recorded with percent weight loss 18.73. In the present study, the hydrolyzates were detoxified by using 2.5% charcoal treatment for improving the fermentation ability. The phenolics 21% were reduced in Sodium hydroxide hydrolyzate. The reducing sugars in hydrolyzate were then fermented by Metschnikowia sp. Y31, Metschnikowia cibodasensis Y34 and Saccharomyces cerevisiae K7 (used as standard yeast). The reducing sugars observed after NaOH, KOH and Ca(OH)2 hydrolysis and then after fermentation observed (%v/v) 3.52±0.01(on day 9), 3.16±0.01 (on day 8), and 3.33±0.01(on day 7) ethanol respectively by Metschnikowia sp. Y31 and 2.65±0.01(on day 1), 2.63±0.01(on day 9), 3.36±0.01(on day 1) % ethanol correspondingly by Metschnikowia cibodasensis Y34 yeast. While with Saccharomyces cerevisiae K7 the yield was 2.12±0.01, 1.71±0.01, 3.04±0.01 (%v/v) ethanol on day 1. Maximum ethanol yield (% v/v) i.e. 3.52±0.01 was observed in sodium hydroxide hydrolyzate having reducing sugar 5.23±0.02 on 9th day by Metschnikowia sp. Y31 while in yeast Metschnikowia cibodasensis Y34 maximum ethanol yield (3.36) on day 1. This predicted that both yeasts are ethanol tolerant. However, Metschnikowia cibodasensis Y34 appeared as promising candidate to produce ethanol in minimum days.