PRODUCCIÓN DE BIOGÁS Y CARACTERÍSTICAS FERMENTATIVAS in vitro DE CONSORCIOS BACTERIANOS CELULOLÍTICOS RUMINALES OBTENIDOS DE DIFERENTES FIBRAS

Abstract

<p><strong>Background</strong>. Cellulolytic bacterial consortia (CBC) serve as additives to improve fiber degradation in ruminants, since they improve biogas production and <em>in vitro</em> fermentation characteristics. <strong>Objective</strong>. To evaluate the biogas production and fermentative characteristics <em>in vitro </em>of mulato grass inoculated with ruminal CBC obtained from ground sawdust, ground mulato grass or whole stem as substrates in the selective culture medium. <strong>Methodology</strong>. The CBC were obtained from ruminal fluid from a Suiz-Bu cow fitted with a ruminal cannula, which was transferred six times in a selective anaerobic medium. The test consisted of preparing sterile biodigesters with 0.5 g of mulatto grass with 63 d of regrowth, 45 mL of culture medium. The inoculation was with 5 mL of a type of CBC. The biodigesters were incubated 72 h at 39 °C. Biogas production was measured at 3, 6, 9, 12, 24, 48 and 72 h. In the culture media, ammonia nitrogen (N-NH<sub>3</sub>), total bacterial count, cellulase activity, pH, dry matter degradation (DMD) and neutral detergent fiber degradation (NDFD) were determined at 12, 24, 48 y 72 h. In the biogas production a completely random design was used; while in the rest of the variables a completely randomized design was carried out with a 3x4 factorial arrangement, with fiber source and incubation time as factors. <strong>Results</strong>. The biogas production of the CBC obtained from the ground grass showed higher (p<0.05) accumulated production in all the evaluated times. The CBC obtained from sawdust increased the biogas production by 175% from 24 to 48 h and by 313% from 48 to 72 h. There was an interaction effect (p <0.05) on DMD, NDFD, N-NH<sub>3</sub>, total bacterial count and cellulase enzymatic activity. The CBC obtained from ground mulatto grass at 72 h increased (p <0.05) the DMD and NDFD. The CBC obtained from sawdust increased DMD by 19.1% and NDFD by 33% from 48 to 72 h. The concentration of bacteria in the observed interactions is within the range of the ruminal ecosystem. The highest (p<0.05) content of N-NH<sub>3</sub> was determined when the CBC obtained from grass stem with 12, 24 and 72 h of incubation were used. <strong>Implications</strong>. Using the same fiber source to obtain the CBCs improves the degradation of said fiber. <strong>Conclusion</strong>. The size and source of fiber are decisive in the type of bacteria that make up the cellulolytic bacterial consortia of ruminal origin under the conditions of this <em>in vitro</em> test.</p>