**5. Ways of mitigating the problems associated with EPS production by**  *Lactobacillus* **spp.**

A critical look at available scientific literature has shown that the importance of *Lactobacillus* EPS in medicine and industries cannot be overemphasized. It is therefore important that serious research and strategies targeted at improving the yield and manipulating its structures to achieve desired properties be the focus of scientists.

### **5.1 Screening for high EPS yielding strains**

Badel et al. [63] in their study suggested that about 165 spp. of *Lactobacillus* are capable of EPS production [63]. Having identified these spp., there is then a need for extensive screening of these spp. to identify strains with potentially high EPS yielding capacity. It is a known fact that EPS are produced by these organisms to help them withstand environmental stress. Based on this fact it is, therefore, possible to experimentally create some of these stress conditions in the laboratories to enhance EPS production by the potentially high yielding strains. The stress may be in the form of deprivation or excessive introduction of certain nutritional substances. Organisms are known to respond differently to these challenges. A typical example is shown with *Lactobacillus lactis* subsp. cremoris and *Lactobacillus delbreckii* subsp. bulgaricus. While nitrogen deprivation improved the yield of EPS by *L. lactis* subsp. *cremoris* [64], nitrogen enrichment caused an improved EPS production by *Lactobacillus delbreckii* subsp. *bulgaricus* [65]. Similarly, sugar stress has also been shown to affect EPS production by *Lactobacillus* spp. It has been established that an increase in the concentration of sucrose in various media for the growth of *Lactobacillus* spp. has resulted in a significant increase in EPS production by the organisms [66–68]. Other stress conditions that enhance EPS production include osmotic stress [66] and temperature stress [69]. The stress-induced by the presence of other organisms has also led to enhanced EPS production. Several studies have shown that co-cultivation of some strains of *Lactobacillus* spp. with *Saccharomyces cerevisiae* led to improved production of EPS [70–72].

#### **5.2 Development of genetically engineered strain**

The advent of biotechnology and molecular biology has led to finding solutions to certain biological and physiological problems. Genetic engineering being the modification of organisms or population of organisms through manipulation or recombination of DNA or other nucleic acid molecules has led to the discovery of important substances such as human insulin and important vaccines. Due to the increasing importance of EPS in medicine and industries, a good understanding of genes encoding EPS production and their biosynthetic pathways has become very necessary. These studies have shown that there are four pathways involved in EPS production namely wzy-dependent pathway, the ATP-binding ABC transporter pathway, the synthase-dependent pathway, and extracellular synthesis by sucrose-dependent pathway [73]. *Lactobacillus* spp. are known to produce EPS via the wzy-dependent pathway [74]. Genetic engineering technology can enhance EPS production through manipulation of carbon metabolism and regulation of the biosynthetic pathways for its production [75]. Genetic manipulations leading to overexpression of genes and gene knockouts have caused an increase and structural changes in the produced EPS with desired characteristics.

#### **5.3 Exploration of efficient extraction method**

The production of a high yield of EPS requires optimization of the media for the growth of the bacteria. This involves the addition of substances to the established

media for the growth of the bacteria. These additional substances aimed at enhancing EPS production may pose serious problems during the recovery of the final products. Therefore, successful production can be said to rely substantially on the use of a medium that not only allow high yield but also one whose components do not interfere with EPS component, recovery, and quantification [76]. In choosing a media it is advisable to choose one whose components are defined with minimal interfering compounds. Based on the complexities (no of additional substances for enrichment) of different media the more laborious the extraction/purification of the EPS. In complex media, a lot of pre-treatments and treatments are usually carried out. It is important to state that the use of complex media for a supposed gain in yield should be weighed against the laborious processes of the final recovery. This is because the possible gain in yield could be lost in the high cost and laborious processes of recovery. At times simple media may give substantial yield without the rigorous processes of recovery involved in the use of complex media. In all, the optimal recovery of the produced EPS should be the desire of the whole process.
