Lies Dwiarti

Production of l-lactic acid from corncob

The optimum temperature, initial pH, amount of added enzyme and substrate (corncob) for the hydrolysis of corncob by Acremonium cellulase were 35 degrees C, 4.5, 10 u/g-corncob and 100 g/l, respectively. Under the optimum conditions, more than 55 g/l of reducing sugars were hydrolyzed from 100 g/l of corncob to 34 g/l of glucose and 12 g/l of xylose based on dried corncob. More than 25 g/l of L-lactic acid was produced from this enzymatic hydrolyzate and less than 5 g/l of xylose remained in the 3-l airlift bioreactor. The production of L-lactic acid by simultaneous saccharification and fermentation (SSF) was also carried out in the 3-l airlift bioreactor using Acremonium thermophilus (cellulose-producer) and Rhizopus sp. MK-96-1196 (lactic acid-producer). More than 24 g/l of L-lactic acid was produced from 100 g/l of untreated raw corncob.

Optimization and scale-up of L-lactic acid fermentation by mutant strain Rhizopus sp. MK-96-1196 in airlift bioreactors

We determined the optimum culture conditions such as inoculum size, initial starch concentration, pH during the fermentation and aeration rate for L-lactic acid production by Rhizopus sp. MK-96-1196 in a 3-l airlift bioreactor. More than 90 g/l of L-lactic acid was produced from only partially enzymatically hydrolyzed corn starch with a production rate of 2.6 g/l/h and a product yield of 87% based on the starch consumed under the optimum conditions in the 3-l airlift bioreactor. Scale-up from the 3-l to a 100-l airlift bioreactor for L-lactic acid fermentation was carried out using V(s)(cm/s) as a scale-up criterion. The production rates and yields of L-lactic acid in both bioreactors appeared to be fairly well correlated with k(L)a (1/h).

Isolation of Ashbya gossypii mutant for an improved riboflavin production targeting for biorefinery technology

Aims:  To isolate a strain overproducing riboflavin and to improve riboflavin production for practical use in a biorefinery technology.

Enhancement of lipase catalyzed-fatty acid methyl esters production from waste activated bleaching earth by nullification of lipase inhibitors

This study sought to identify inhibitory factors of lipase catalyzed-fatty acid methyl esters (FAME) production from waste activated bleaching earth (wABE). During the vegetable oil refinery process, activated bleaching earth (ABE) is used for removing the impure compounds, but adsorbs vegetable oil up to 35-40% as on a weight basis, and then the wABE is discarded as waste material. The impurities were extracted from the wABE with methanol and evaluated by infra-red (IR) spectroscopy, which revealed that some were chlorophyll-plant pigments. The chlorophylls inhibited the lipase during FAME conversion from wABE. The inhibition by a mixture of chlorophyll a and b was found to be competitive. The inhibition of the enzymatic hydrolysis of waste vegetable oil contained in wABE by chlorophyll a alone was competitive, while the inhibition by chlorophyll b alone was non-competitive. Furthermore, the addition of a small amount of alkali nullified this inhibitory effect and accelerated the FAME production rate. When 0.9% KOH (w/w wABE) was added to the transesterification reaction with only 0.05% lipase (w/w wABE), the maximum FAME production rate improved 120-fold, as compared to that without the addition of KOH. The alkali-combined lipase significantly enhanced the FAME production rate from wABE, in spite of the presence of the plant pigments, and even when a lower amount of lipase was used as a catalyst.