Conversion of agro-industrial corn and coconut by products into higher value-added products

Abstract

Agro-industrial by-products such as corn cobs, corn fiber, coconut debris and coconutfiber can be converted into high quality products such as glucose, xylose and xylitol,involving two important conversion processes: acid hydrolysis using sulfuric acid (H2SO4)and yeast fermentation. Prior to acid hydrolysis, delignifying the samples with alkali isnecessary as it can reduce lignin interferences. Results clearly showed that the lignin removalfrom corn cobs, corn fiber, coconut debris and coconut fiber were 30.12??0.37, 37.71??0.71,40.52??0.85 and 27.92??0.47%, respectively. However, the delignification process might alsoreduce the glucose and xylose contents from acid hydrolysates. In this study, the sampleswere hydrolyzed using 1, 3, 5 and 7% (v/v) H2SO4 with a ratio of 1:15 (g sample: mL acid)at 100??C for 1 hour. It was found that maximum sugar contents from corn cobs and corn fibercan be obtained from the 3% H2SO4 treatment, while those from the coconut debris andcoconut fiber were at 5% H2SO4. As determined by HPLC technique with the hydrolysatesobtained by these conditions, it demonstrated that the glucose and xylose yields from corncobs, corn fiber, coconut debris and coconut fiber were 9.72??0.86 and 9.91??0.51%,3.46??0.14 and 10.70??0.12%, 0.22??0.12 and 2.53??0.33%, and 5.65??0.15 and 5.28??0.5%(w/w), respectively. During acid hydrolysis, however, inhibitory substances such as furfural,hydroxymethylfurfural and phenolics were simultaneously formed, accordingly,detoxification may then be required. The findings of a study of detoxification were thattreatments with activated charcoal can reduce furfural and phenolic compounds but somesugars would be partially lost. An ion exchange chromatographic method would be moreappropriate since it can minimize a number of these compounds into levels which can do noharm to fermenting yeasts (i.e. Saccharomyces, Candida spp.) as well as eliminating sugarloss.

Keywords: acid hydrolysis, xylose, glucose, by-products