Two types of induction treatments (heat-shock pretreatment, HSP, and acetylene, Ac), inocula (meso and thermophilic) and incubation temperatures (37 and 55 degrees C) were tested according to a full factorial design 23 with the aim of assessing their effects on cumulative H-2 production (P-H, mmol H-2/mini-reactor), initial H-2 production rate (R-i,(H), mu mol H-2/(g VSi x h)), lag time (T-lag, h), and metabolites distribution when fermenting organic solid waste with an undefined anerobic consortia in batch mini-reactors. Type of inocula did not have a significant effect on P-H, T-lag, and R-i,(H) except for organic acids production: mini-reactors seeded with thermophilic inocula had the highest organic acid production. Concerning the induction treatment, it was found that on the average Ac only affected in a positive way the P-H and T-lag. Thus, P-H in Ac-inhibited units (6.97) was 20% larger than those in HSP-inhibited units (5.77). Also, Ac favored a shorter T-lag for PH in comparison with HSP (180 vs. 366). Additionally, a positive correlation was found between H-2 and organic acid production. In contrast, solvent concentration in heat-shocked minireactors were slightly higher than in reactors spiked with Ac. Regarding the incubation temperature, on the average mesophilic temperature affected in a positive and very significant way P-H (10.07 vs. 2.67) and R-i,R-H (2.43 vs. 0.76) with minimum T-lag (87 vs. 459). The positive correlation between H-2 and organic acids production was found again. Yet, incubation temperature did not seem to affect solvent production. A strong interaction was observed between induction treatment and incubation temperature. Thus, Ac-inhibited units showed higher values of P-H and R-i,R-H than that HSP-inhibited units only under thermophilic incubation. Contrary to this, HSP-inhibited units showed the highest values of P-H and R-i,R-H only under mesophilic conditions. Therefore, the superiority of an induction treatment seems to strongly depend on the incubation temperature. (c) 2006 Wiley Periodicals, Inc.