Hydrolysis of Pretreated Prosopis juliflora Stem to Simple Sugars using Immobilized Enzymes

  • Wiseman Ngigi Moi University
  • David Menzwa Moi University
  • Ambrose Kiprop Moi University

Abstract

ABSTRACT- Prosopis juliflora is a noxious weed which can be put into profitable use and help address the use of food based substrates in the production of glucose which lead to food insecurity. In an attempt to find profitable use, Prosopis juliflora stem was investigated for its potential to produce glucose. In this research, Prosopis juliflora stems were dried and milled into fine powder to pass through a 0.5mm screen followed by alkali pretreatment then hydrolysis using immobilized enzymes. The enzymes used were cellulase, hemicellulase and cellobiase. Cellobiase was immobilized using sodium alginate while cellulase and hemicellulase were immobilized covalently using glutaraldehyde (GA). The factors studied were pH, temperature, time and concentration of sodium alginate (NaAl). The level of pH was varied at 4.5 - 7.5, temperature varied at 40 - 70°C, time varied at 2- 72 hours while NaAl concentration of was varied at 1.0% - 3.0% (w/v). The maximum hydrolysis yield was established using a Central Composite Rotatable Design (CCRD) in Response to Surface Methodology (RSM). Mathematical models estimating the yield of simple sugars from Prosopis juliflora stem were developed and analyzed for predicting and enhancing the yield of glucose.Optimum glucose yield of 78.2% (w/w) was obtained from Prosopis juliflora stem at 55°C hydrolysis temperature, pH of hydrolysis medium of 6.0, 2.0 % (w/v) concentration of sodium alginate (w/v) and 48 hours hydrolysis period. Lowest glucose yield of 43.1% (w/w) was obtained at 55°C hydrolysis temperature, pH of hydrolysis medium of 6.0, 3.7% (w/v) concentration of sodium alginate and 48 hours hydrolysis period. The immobilized enzyme was easily separated through simple filtration, washed and recycled from the hydrolysis reaction mixture after each hydrolysis reaction cycle of 48 hours. When reused in subsequent hydrolysis reactions, the immobilized enzyme retained enzymatic activity in subsequent substrate hydrolysis batches by upto 10 cycles as demonstrated by the yield of glucose of 57.6% (w/w). The yield of glucose obtained from the hydrolysis of Prosopis juliflora stem( 78.2%, w/w) using immobilized enzymes indicate that Prosopis juliflora stem is suitable for the production of glucose which can be used to produce bioethanol and marketable chemicals such as citric and lactic acid. In addition the ability to recycle the immobilized enzymes contributes significantly towards bringing down the cost of enzymatic hydrolysis.
Published
Jun 13, 2016
How to Cite
NGIGI, Wiseman; MENZWA, David; KIPROP, Ambrose. Hydrolysis of Pretreated Prosopis juliflora Stem to Simple Sugars using Immobilized Enzymes. Proceedings of Sustainable Research and Innovation Conference, [S.l.], p. 238-249, june 2016. ISSN 2079-6226. Available at: <http://sri.jkuat.ac.ke/ojs/index.php/proceedings/article/view/434>. Date accessed: 23 nov. 2017.

Keywords

Central Composite Rotatable Design (CCRD); glucose; hydrolysis; Prosopis juliflora