Microbial Lactic Acid Production from Renewable Resources - Sustainable Biotechnology: Sources of Renewable Energy - page 220

productivity. Very high volumetric lactic acid productivity (9.72 g/l h) was obtained

from glucose with a two-stage immobilized packed-bed system by Lb. casei CRL
686 [50].

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4.1 Cheese Whey

Whey is a waste stream of cheese production which contains lactose, protein, fat,
and mineral salts. Deproteinized whey contains mainly lactose and recently has been
extensively studied for lactic acid production. Theoretically, 4 moles of lactic acid
could be obtained when lactose is broken down directly into glucose and galactose
via a permease system, which are both converted to two moles lactic acid in the
homofermentation pathway. The performance of different microorganisms for lactic
acid production from cheese whey is shown in Table 2. Genus Lactobacillus is the
main lactic acid producer which not only utilizes lactose with high conversion rates
but also utilizes other nutrient such as protein present in whey [68]. The highest
lactic acid productivity of 6.34 g/l

h and yield of 0.98 g/g lactose were obtained
using the cell-recycle repeated batch production by Lb. sp. RKY2 [66]. High lactic
acid yield (0.93 g/g lactose) and productivity (3.97 g/l

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h) were also obtained with
Lb. c asei NRRL B-441 in a batch operated fermentation reactor [63].
Genus Lactococcu , like Lc. lactis , have been and are still being extensively stud-
ied due to their commercial potential for converting sugar to lactic acid. Lc. lactis
subsp .cremoris 2487 could consume 99.1% lactose in the whey permeate and the
highest lactic acid yield and productivity obtained with this strain were 0.88 g/g
lactose and 4.6 g/l

h, respectively [67].
B. longum can also convert lactose into high-quality lactic acid although minimal
research have been focused on this genus. Lactic acid yield of 0.81 g/g lactose was

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Ta b l e 2 Performance of microorganisms and processes on lactic acid production from cheese
whey

Yield (g/g
sugar)

Productivity
(g/l · h) Microorganisms Process References

B. longum NCFB 2259 Batch,
semi-continuous,
or immobilization

0.51-0.82 0.3-0.7 [20, 62]

Lb. casei NRRL B-441 Batch 0.93 2.5-3.97 [63]

Lb. casei SU No 22 Fed-batch and

immobilization

0.32-0.39 2.0 [36]

Lb. helveticus ATCC
15009

Batch 0.66 2.7 [64]

Lb. helveticus Batch and

immobilization

10.5 [65]

Lb. sp. RKY2 Batch and repeated

batch cultures

0.98 6.34 [66]

Lc. Lactis sp. Cremoris
2487

Batch 0.88 4.6 [67]