Suitability of various plant derived gelling agents as agar substitute in microbiological growth media
Eleven putative gelling agents were investigated as agar substitutes. These included arrowroot (Maranta arundinaceae), coconut powder (Cocos nucifera), corn flour (Zea mays var. amylacea), gel rite (a water-soluble polysaccharide produced by Sphingomonas elodea), glue (Cyanoacrylates), katira gum (Cochlospermum religiosum), guar gum (Cyamopsis tetragonolobus L.), isubgol husk (Plantago ovata), pectin and rice (Oryza sativa L.) powder. Among these, guar gum was found a promising alternate candidate for agar. Media solidified with 2.8% guar gum was transparent and supportive for the growth of three test fungi (Trichoderma harzianum, Alternaria alternata and Alternaria solani) as good as agar. Guar gum also excelled in terms of cost benefit ratio when compared with agar. Guar gum fortified media was found to cost $ 0.005/L as compared to agar supplemented media costing $ 1.17/L. Further, guar gum is easily available and can be added with ease thereby serving as a suitable and inexpensive substitute of agar and thus, can be adopted for routine microbiological testing in resource poor countries.
Key words: Guar gum, media, agar, gelling agents.