Application of Apple pomace for Fungal Cultivation
Abstract: Apple pomace is a solid by-product acquired from pressing and crushing millions of tons of apple in juice-industries. It represents 25-30 % of the original fruit and consists of peels, seeds and pulp. This raw material has multiple applications due to its high carbohydrate and moisture content. This bachelor thesis evaluated the use apple pomace acquired from Herrljunga cider for the cultivation of a filamentous fungus to produce biomass and ethanol. Different pretreatment strategies were applied to the apple pomace to extract as much sugars as possible. Several batches were made by mixing pomace and distilled water at different ratios (g pomace per g water) and different water temperatures. Apple juice was produced by filtering soaked pomace using a fine fabric. Apple pomace suspensions were made by adding pomace and water without mixing it (non-homogenised) and homogenised suspensions by mixing with a kitchen blender. Some apple juice batches were pH adjusted to 5.5 to investigate the effect on the fungal growth. The batches were put in Erlenmeyer flasks, sterilised and inoculated with the fungal strain Rhizomucor that has been isolated from Indonesian leaves used for tempe preparation. The Erlenmeyer flasks were incubated in a water shake for 72 h. Samples were taken every 24 h to follow sugar and ethanol concentrations. The samples were analysed by HPLC (High-Performance Liquid Chromatography). The results showed that apple pomace suspension did not perform well compared to the apple juice since the suspension was too viscous and lacked oxygen for the fungus to grow properly in the solution. The apple juice did show a significant improvement compared to the suspension, however pH adjustment to 5.5 had a negative impact on the fungal growth. Cold pre-treatment with an apple pomace to water ratio of 1 g pomace /g water produced the most biomass, with a yield of 9.7 g biomass per kg dry apple pomace. For ethanol production, an apple pomace to water ratio of 1 g pomace /g water using hot water had the highest yield of 11.2 g ethanol per kg dry apple pomace.
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