Indian Journal of Animlll Sciences 74 (2): 211-215, February 2004 Effect of fungi and N-fixing bacteria on the solid state fermentation of rice straw SHARMILA RANEI, A K PUNIYN and KlSHAN SINGI-P National Dairy Research Institute, Kamal, H aryana 132 001 I ndi a Received: 20 November 2002; Accepted: 20 OctoDer 2003 ABSTRACT SSF of rice straw carricd outio/" 7 days at 65% moisture content, with and without Phanerochllele chrysasporiu/Il, p as/rea/us Caprmllsfimetarius (3 and 5%) in combination ofAzQ.I'pirellllm bmsilense and Azatobac/(n' chmo('()cculll (3 and 5% ]()R_I09 cells/ml), Ancr the jcrmcntation period, the SSF were evaluated for different parameters. Rice had nlllIal pH, CP conte.Ilt, DM and digestibility of 5,30,3,80, 91.20 and 35.()O% respectively. The value:> for different. parameters changed with P. clllysosporiu/Il, P. and C. fimeturills along with asymbiotic nitrogen-fixers (/I, bras,[ellse and A. clzroococcum). Maximum DML (4.59%) Was observed ill straw with P as/reatlls with A. hrasilense. The digestibility and CP content of straw aner inoculation with P os/rea/lls and A. bra.l'ilen.l'lI was in range of 49.57 to 50.00 and 4.82 to 5.88% respectively. The lowering of the ADL value from an initial value of 6.64 to 6.30% in straw alTccted the biodegradation place during the SSF. Thc highest PE obs1lrved in straw (2.18%) was due to the synergistic growth of P. astreallls and 11. brasilellse during the SSF. Key wOl'ds: Fungal culturcs, N-fixing bacteria, Rice straw, SSF Utilization of fibrous crop residues by ruminants as a source of energy is limited, because the rumen microbial population docs not posses lignolytic activity. Although these contain more than 60% of their dry matter the form of cellulose and hemicelluloses, their digestibility IS very poor. As a result, a large proportion of the potential energy in lignified crop residues remains unutilized. Recent microbial technology providing more efficient micro- organisms and innovative solid state fermentation (SSF) technology is expected to be more appropriate for the biological conversion oflignocellulosic wastes into feed with higher nutritive value, The product also gets enriched in fats, soluble sugars, vitamins, amino acids and thus can be used entirety as animal feed. However, supplementation with Inorganic nitrogen is necessary to build up biomass protein. Since none of the lignocelluloscs degrading fungi has the ability of fixing molecular nitrogen, atmospheric nitrogen cannot be used as a source for the biosynthesis of protein. Hence, asymbiolic nitrogen-fixing bacteria can be used to convert molecular nitrogen into biomass protein and these also .aid in solubilising substrate at a faster rate, thereby helpmg in establishing the lignocellulolytic fungi (Halsall and Gibson 1989). Therefore the present study is undertaken to know the effect of fungus and N-fixing bacteria on the SSF of rice straw. . address: IPh.D. Scholar, 2S en ior Scientist, lPrincipal SCJentlst, Dairy Microbiology Division. MATERIALS AND METHODS The fungal cultures of Phanerochaete chfysosporium, Pleurotus ostreatus, Coprinus jimetarius and Azotobacter chroococcum used in this study were obtained from Fungal Biotechnology Laboratory, Dairy Microbiology Division, National Dairy Research Institute, Karnal. The bacterial cultures Azospirillum brasilense was obtained fr0111 microbiology depatiment, Chaudhary Charan Singh Harynna Agricultural University, Risar. Fungal cultures were grown on malt extract agar for 5-7 days at 30-3 SoC and stored at refrigerated (S-7°C). A. chroococcum andA. brnsiJense were maintained on Jensen's medi urn. Spawn culture of fungi was prepared on millet (sorghum) seeds (Kumar and Singh 1990). Washed cell suspension ofA. brasilense andA. chroococcum (10 8 -10 9 cells Iml) were prepared in sterile distilled water by scrapping the 7 day old growth on agar sUlface. Rice straw (25 g) was taken in polypropylene bags (17 x 25 cm), Moisture content was adjusted to 65% (v!w) and capped with cotton plugged pOlystyrene lids. The bags were sterilized and inoculated with millet-based inoculums (3 and 5%) of fungal cultures along with bacteria (3 and 5%). The bags were incubated at their respective temperatures for 7-10 days. After the incubation, the biomass was dried (105°C), milled (particle size, <1 rum) and used for pH, dry matter loss (DML), NDF, ADF, ADL, CP and NBDMD analysis (Kumar and Singh 1990, Agosin and Odier 1985, AOAC 1984, Goering and Van Soest 1970, Mehrez