Kefiran is a functional exopolysaccharide produced by originated from kefir, traditional fermented milk in the Caucasian Mountains, Russia. Kefiran is attractive as thickeners, stabilizers, emulsifiers, gelling agents and also has antimicrobial and antitumor activity. However, the production costs of kefiran are still high mainly due to high cost of carbon and nitrogen sources. This study aimed to produce kefiran and its co-product, lactic acid, from low-cost industrial byproducts. Among the sources tested, whey lactose (at 2% sugar concentration) and spent yeast cells hydrolysate (at 6 g-nitrogen/L) gave the highest kefiran of 480 ± 21 mg/L along with lactic acid of 20.1 ± 0.2 g/L. The combination of these two sources and initial pH were optimized through Response Surface Methodology. With the optimized medium, produced more kefiran and lactic acid up to 635 ± 7 mg/L and 32.9 ± 0.7 g/L, respectively. When the pH was controlled to alleviate the inhibition from acidic pH, could consume all sugars and produced kefiran and lactic acid up to 1693 ± 29 mg/L and 87.49 ± 0.23 g/L, respectively. Moreover, the fed-batch fermentation with intermittent adding of whey lactose improved kefiran and lactic acid productions up to 2514 ± 93 mg/L and 135 ± 1.75 g/L, respectively. These results indicate the promising approach to economically produce kefiran and lactic acid from low-cost nutrient sources.
Empty fruit bunch (EFB) is one of lignocellulosic wastes from palm oil mill. They are attractive feedstocks for production of fermentable sugars due to their low cost, renewable nature and abundance. Biological pretreatments employ microorganisms mainly fungi to reduce lignin and increase cellulose content prior to hydrolysis of cellulose into fermentable sugars. In this study, oleaginous fungi Aspergillus tubingensis TSIP9 with cellulolytic enzymes was used as potent microorganism for biological pretreatment of EFB through solid state fermentation (SoSF). The effluent from anaerobic digester (biogas effluent) was used as nutrient sources and moisturizing agents. After optimization in SoSF bioreactor, the cellulose content in EFB was increased from 40.58 ± 0.99% up to 61.24 ± 0.05% and this process also produced lipids of 115.8 ± 3.24 mg/g-EFB and cellulolytic enzymes of 20.00 ± 1.11 U/g-EFB. This study has shown that it was possible to biorefinery palm oil mill wastes into valuable cellulose pulp, microbial lipids and enzymes with the low-cost, practical and environmental friendly process.
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