摘要：Poly Laevo Lac.ic.Ac.d (PLLA), in spite of being an exc.llent bioplastic. has exorbitantly high m.rket pric. due to the high c.st of raw m.terial (lac.ose, gluc.se, suc.ose). Henc., its m.nufac.ure is being attem.ted starting from.waste effluents suc. as c.eese whey and m.lasses. Earlier studies on the sam. in fluidized bed and sem.fluidized bed biofilm.reac.ors yielded enc.uraging results. The present study therefore involves design and analysis of inverse fluidized bed biofilm.reac.ors for lac.ic.ac.d synthesis. The perform.nc. features of the bioreac.or have been studied both m.them.tic.lly as well as experim.ntally. The inverse fluidized bed biofilm.reac.or has been found to provide m.re than 75% c.nversion of suc.ose/lac.ose even at high c.pac.ties (high feed flow rates) exc.eding 56,000 L/hr, within a reasonably low reac.or volum.. The frac.ional substrate c.nversion inc.eases, though sluggishly, with inc.ease in feed flow rate due to bed expansion and also with inc.ease in c.ll m.ss c.nc.ntration in biofilm.due to enhanc.m.nt in intrinsic.rate of bioc.nversion. The inverse fluidized bed biofilm.reac.or of proposed design c.uld be safely rec.m.ended for the c.m.erc.al synthesis of polym.r grade lac.ic.ac.d from.waste effluents suc. as c.eese whey and m.lasses. The low operating c.st of the bioreac.or (due to downflow m.de of operation) enhanc.s the ec.nom. of the proc.ss. This would also help in signific.ntly lowering the m.rket pric. of the green plastic.(PLLA) and shall prom.te its large sc.le m.nufac.ure and utilisation.