L(+) lactic acid was directly produced in a three-stage membrane-integrated hybrid reactor system starting with a cheap, renewable and clean carbon source. Provision of flat sheet cross flow membrane modules for microfiltration and nanofiltration permitted selective production of L(+) lactic acid under high cell density with recycling of cells and unconverted sugars. This modular design ensured high yield (0.96 gg(-1)), productivity (12.4 g L-1 h(-1)), concentration (250 g L-1) and purity (95%) in a very simple, environmentally benign, compact and flexible plant configuration reflecting all the major characteristics of high process intensification. Such process intensification has been analysed for the first time in terms of space intensification, application flexibility, capacity flexibility, energy reduction parameter and cost advantage parameter. The value of space intensification parameter, energy reduction parameter and cost advantage parameter that were computed to be 3.33, 0.022 and 0.35 respectively indicated high degree of process intensification in such a novel and green production scheme. (C) 2012 Elsevier B.V. All rights reserved.