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Abstract:Need for large quantity of bacterial cellulose (BC), used as a matrix for production of numerous materials with desirable properties, has increased in the fields of biomedicine and electronics. To achieve the goals further investigations are essential in order to understand the intracellular polymerisation reaction; to increase the biosynthesis rate and reduce cost of the overall production process. Carbon sources for the BC production are usually glucose, fructose, and sucrose, so juices from low grade fruits can successfully substitute the carbohydrates, vitamins, ascorbic acid, and proteins in the growth medium and can form low-cost substrates. We used strain Gluconoacetobacter xylinus CICC10529 to produce cellulose from watermelon and mandarin juices (70% v/v and 80% v/v) with or without yeast extract supplement. The liquid media (with working volumes 50 mL and 100 mL) made from fruit juices always contained MgSO 4 .7H 2 O (1.5 w/v%), K 2 HPO 4 (0.1 w/v%), as well as ethanol (1 v/v%). Two modes of operation: static biosynthesis in incubator and dynamic biosynthesis in orbital shaker (at 200 rpm) were conducted at 30°C. The production process was monitored during 7 to 10 days. Thermal properties of BC produced at different conditions were investigated through thermal gravimetric analysis and width of the cellulose fibrils/ribbons were compared via microscopic observations.

Coconut coir is composed of cellulose, lignin, pectin, and hemicellulose. Production of biofuels is one possible application of this lignocellulosic waste. Physical-chemical pretreatment is required in order to remove lignin and to increase cellulose digestability. Commonly, the coconut coir was pretreated primarily with NaOH solution (5-11%) in autoclave at 121°C for 1 hour. The aims of this work were to find an enhanced pretreatment procedure for the coconut coir, and to study kinetics of the cellulose hydrolysis process at elevated temperature. For this purpose, we used NaOH solution (5% w/v) and ultrasonic bath for 1 hour at 50°C, which can successfully replace autoclave pretreatment. Moreover, the temperature of the ultrasonic pretreatment coincided with the temperature of hydrolysis reaction carried out subsequently. Two commercial enzymes cellulase and β-galactosidase were applied simultaneously as biocatalyst for the enzymatic hydrolysis of cellulose. One of the advantages of the ultrasound-assisted pretreatment was the lowest weight loss of the coir -48% (w/w). When using autoclave, the weight loss was much higher -about 66-67% (w/w) of the coir samples. First order kinetic equation for the enzymatic hydrolysis of cellulose to glucose was derived, and kinetic constants were obtained for the product released at different modes of operation.