Abstract
A study was carried out on yeast fermentation of carica papaya (pawpaw) agricultural waste using dried active baker's yeast and brewer's yeast strain (Sacchromyces cerevisiae). The pawpaw considered as an agricultural waste was the tapped ripe pawpaw fruit harvested after the tapping of papain. Effect of different yeast strains on the percentage yield of ethanol was investigated. The effects of yeast concentration, saccharification and different nutrient supplements as they relate to the optimization of the ethanol yield were also carried out. The fermented pawpaw yielded ethanol contents of 3.83 to 5.19% (v/v). The reducing sugar in the pawpaw was determined before and after saccharification. The reducing sugar was highest after 48 h of saccharification using Aspergillus niger. The value recorded was 7.6 to 13.6 g/100g. Brewers yeast gave a higher ethanol yield than bakers yeast. Saccharification for 48 h coupled with nutrient supplements significantly increased the ethanol yield. Key words: Paw-paw agrowaste, bakers yeast, brewers yeast, fermentation, pH, temperature, saccharification.
Highlights
Carica papaya is one of the fruits commonly used as food and medicine in Nigeria
Pawpaw fruits were obtained from National Research Institute for Chemical Technology (NARICT), Zaria papain experimental garden
A. niger's concentration used was 1.96 x 106 cells/5 ml. b0 h means the A. niger and the S. cerevisiae were added simultaneously. c24 h represent the period of saccharification before the S. cerevisiae was added. dResults are means of duplicate experiment
Summary
Carica papaya (pawpaw) is one of the fruits commonly used as food and medicine in Nigeria. It is eaten as fresh fruit or processed into deserts (Desmond, 1995). The unripe matured pawpaw fruit is used for the production of papain by the making of incisions on the back of the fruits to get the latex for the papain production. With the increasing value of these petrochemical feedstocks, fermentation of ethanol is bound to receive more attention (Ahmeh et al, 1988). In this regard, use of renewable materials would be more economical, since they are cheaper and available. We attempt to process the fruit waste into alcohol, which will have industrial applications
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