Environmental Engineering Reference
In-Depth Information
Microbial Lactic Acid Production
from Renewable Resources
Yebo Li and Fengjie Cui
Abstract
Lactic acid is widely used in the food, chemical, textile, and pharmaceu-
tical industries. New applications of lactic acid for the manufacture of biodegradable
polymers have increased the demand for it. Lactic acid can be produced from cheese
whey and starchy and lignocellulosic biomass via microbial fermentation with lactic
acid bacteria (LAB) or fungi. Pure sugar and cheese whey can be directly fer-
mented by lactic acid bacteria, while liquefaction and enzymatic saccharification
of starchy biomass and pretreatment and enzymatic hydrolysis of lignocellu-
losic biomass are required for lactic acid production from biomass. Amylolytic
lactic acid bacteria can direct convert starchy biomass to lactic acid. Lactic acid
bacteria and methods used for lactic acid production from different feedstocks are
summarized in this paper. Lactic acid productivity of 6.34 and 4.87 g/l
h and yields
of 0.98 g/g lactose and 0.97 g/g glucose were obtained from cheese whey and wheat
starch, respectively, using cell-recycle repeated batch fermentation by
Lactobacillus
sp
. RKY2. Lactic acid bacteria such as
Lactobacillus pentosus
,
Lactobacillus brevis
and
Lactococcus lactis
can ferment glucose to lactic acid by homolactic fermen-
tation and also effectively convert xylose or arabinose to lactic acid and acetic
acid by heterolactic fermentation. The process for lactic acid production from lig-
nocellulosic biomass needs to be improved to increase the lactic acid yield and
productivity.
·
Keywords
Lactic
acid
·
Microbial
fermentation
·
PLA
·
Lactic
acid
bacteria
·
Biomass
·
Starch
·
Cheese whey
1 Introduction
Lactic acid (2-hydroxypropanoic acid, CH
3
CHOHCOOH) was discovered and
isolated in sour milk in 1780 by the Swedish chemist Carl Wilhelm Scheele (1742-
1786). It is the most widely occurring carboxylic acid in nature and has many
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