Influence of other micro-organisms on the yield of nata [processed food from coconut milk] by Acetobacter aceti sub sp. Xylinum (brown)

Nata de coco in coconut milk medium was prepared from starter obtained from Alaminos, Laguna [Philippines]. The liquor of the nata was plated in coconut water sucrose agar from which micro-organisms were isolated and grouped according to similar morphological and cultural characteristics: Group 1 included all nata forming isolates; Group 2 - the microaerophilic, gram positive, catalase negative rods and cocci; Group 3 - the aerobic gram negative to gram variable, catalase positive short rods and Group 4 the yeast isolates. The non-nata isolates were grown with the best nata isolate (102) in sterilized coconut water broth. Results revealed that certain aerobic bacteria from Group 3 namely: 036, 413 and 420 and yeasts from Group 4 namely 425 and 412 increased the yield of nata. Isolate 036, 413 and 420 increased the yield by 254.7, 243.0 and 169.4% respectively while the yeast isolates 425 and 412 increased the yield by 81.1 and 75.1% respectively over the control. Four starters in unsterilized coconut milk medium from pure cultures of the best isolates from each group were prepared namely: Starter 1 or Control (102); Starter 2 = 413 (+102); Starter 3 = 425 + 413 (102) amd Starter 4 = 425 (+102). These isolates where chosen based on high nata yield and quality. The highest yield was obtained from Starter 3 which showed an increase in yield of 84.4 to 113.3% over the control. On the other hand, Starter 2 exhibited an increase in yield of 31.2 to 35.3% while Starter 4 showed an increase of 15.6 to 32.7%. This implies that a combination of micro-organisms may enhance the growth of nata organism in coconut milk medium. Initial identification suggests that isolate 413 belongs to the genus Acetobacter while the yeast isolate 425 belongs to the genus Saccharomyces.