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BioMed Research International
Volume 2019, Article ID 7212870, 13 pages
https://doi.org/10.1155/2019/7212870
Research Article

High Improvement in Lactic Acid Productivity by New Alkaliphilic Bacterium Using Repeated Batch Fermentation Integrated with Increased Substrate Concentration

1Botany and Microbiology Department, Faculty of Science (Boys), Al-Azhar University, P.N.:11884, Nasr City, Cairo, Egypt
2Microbiology and Industrial Irradiation Division (MIID), Institute of Food and Radiation Biology (IFRB), Atomic Energy Research Establishment (AERE), Ganakbari, Savar, Dhaka-1349, Bangladesh

Correspondence should be addressed to Mohamed Ali Abdel-Rahman; pj.iaduyk@ilademahom

Received 18 September 2018; Revised 22 November 2018; Accepted 6 January 2019; Published 17 January 2019

Academic Editor: Fabiano J. Contesini

Copyright © 2019 Mohamed Ali Abdel-Rahman et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Optically pure lactic acid (LA) is an important chemical platform that has a wide range of industrial and biotechnological applications. Improved parameters for cost effective LA production are of great interest for industrial developments. In the present study, an alkaliphilic lactic acid bacterium, BoM 1-2, was selected among 369 newly obtained bacterial isolates. It was characterized using API 50 CHL kit and identified as Enterococcus hirae BoM 1-2 by 16S rRNA gene sequence analysis. Efficient polymer-grade L-lactic acid production was achieved at pH 9.0 and 40°C. In batch fermentation strategy using 20 g L−1 glucose, 19.6 g L−1 lactic acid was obtained with volumetric productivity of 2.18 g L−1 h−1. While using 100 g L−1 glucose, 96.0 g L−1 lactic acid was obtained with volumetric productivity of 1.07 g L−1 h−1. The highest lactic acid concentration of 180.6 g L−1 was achieved in multipulse fed batch strategy with volumetric productivity of 0.65 g L−1 h−1. To achieve higher productivity, repeated fermentation processes were applied using the two different strategies. In the first strategy, the lactic acid productivity was increased from 1.97 g L−1 h−1 to 4.48 g L−1 h−1 when the total of 10 repeated runs were carried out using 60 g L−1 glucose, but lactic acid productivity decreased to 2.95 g L−1 h−1 using 100 g L−1 glucose. In second strategy, repeated fermentation coupled with gradual increase in glucose concentration from 40 to 100 g L−1 was conducted for 24 runs. A dramatic increase in LA productivity up to 39.9 g L−1 h−1 (18-fold compared to first run) was achieved using 40 g L−1 glucose while volumetric productivity ranging between 24.8 and 29.9 g L−1 h−1 was achieved using 60–100 g L−1 glucose.